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"Snowzilla": A Comprehensive Tucker 1643 Project...

Blackfoot Tucker

Well-known member
GOLD Site Supporter
The blade system is made up of several different components; the blade, the A frame (which has a pivoting frame at the front), the axle mounted frame and the support frame, which is welded to the Tucker. We wanted to keep the overall project moving forward, and so put the A frame aside and concentrated next on the axle mounted frame. We'll get back to the A frame after the machined sleeve arrives.

The factory axle mounted frame was constructed with 3” x 2” tubing with 5/16” wall thickness. That too will be lighter in that we used 1/4” wall tubing. Here’s an in-process photo of our axle mounted frame. The long, top and bottom parallel legs are 13” longer than the factory Tucker legs, and you’ll recall that was to position the hinge points for the A frame in front of the winch. Those parallel legs are one piece. For some reason Tucker made them from two pieces, and we don’t know why. The mounts where it bolts to the bottom of the axle are also being made by my friend back in Vermont, and they’ll be positioned by the back of the “X” frame members. If you look at that frame and think of the forces it has to deal with, it becomes apparent the welded and angled joint behind the “X” is the weak point. Tucker reinforced the frame by welding pieces of 1/4” steel plate on the top and bottom of that joint, overlapping the tube several inches in both directions. They also welded some 1/4” steel plate vertically across the inside of the angle for more reinforcement, and they added some 1 1/2” square tube underneath! Holy Overkill, Batman!

IMG_1632.jpg


We thought of a simpler way, that we think looks better, takes less time and is more than strong enough. The other issue is the axle mounted frame is attached to the underside of the axle, so it hangs underneath and reduces ground clearance. The square tube reinforcement welded to the bottom of the outside frame members reduces that clearance even further. We took some 3” x 3” square tube and mitered the ends to intersect with the back of the “X” leg and the rear angled leg. Then its welded along all sides. We also added the square tube perpendicular to the long frame members in a similar fashion as Tucker did. (If you’re wondering why some pieces have a little surface rust while others don’t, it’s because steel is usually sold in specific lengths. We bought a 20’ stick of 3” x 2” square tube, and that wasn’t long enough. Scott had a remnant from another job (dimensionally identical) and we used part of that, rather than purchase another 20’ when we really wanted about 18”. Yes, one can buy shorter segments from a company such as Metals Supermarket, but the cost is painfully high.)


Another item to point out is the appearance of the welds. Scott has the capability, (equipment and skill) to do various types of welding processes. Typically he uses a MIG welder (Metal Inert Gas), but sometimes he uses stick (or arc). If it’s small detailed work, or a material like aluminum or stainless steel, he’ll use TIG (Tungsten Inert Gas). Yet another process is called dual shield. That uses both a flux core wire and a shielding gas, and that’s what Scott used on the A frame. Rectangular steel tube has rounded corners, rather than sharp, square corners. The thicker the tube, in terms of its wall thickness, the greater the radius of the corners. Thus 1/4” wall tubing has a larger gap at the radius intersection than does 3/16” thick tubing. That gap obviously has to be filled during the welding process.. Often Scott will make two passes; a “root” pass and a “cover" pass. With the A frame, Scott made the root pass with a MIG welder and the cover pass with his dual shield. The dual shield process is very strong and allows the welder to put down quite a bit of material quickly. As I mentioned, the wire has a flux core and that residue has to be removed after welding. But the weld itself looks a little different.


IMG_1653.jpg
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
Getting away from the blade project briefly to discuss yet-to-be-installed upgrades to the steering and hydraulic systems. I'll get back to blade progress soon.

When Scott and I took Thundercat out for its first tests it performed very well, but we uncovered some issues with the steering system. Before coming up with our own solution, I called Tucker and spoke with Jeff Godard to pick his brain. We subsequently made these changes to Thundercat, but Scott and I thought Snowzilla would benefit as well, so we'll incorporate them when we install the modified hydraulic tank and the hydraulic components for the six-way blade.

A cardinal rule of Tucker operation is DON’T turn the steering wheel unless the machine is moving - as you'll potentially over-stress the steering system components. Our problem was that even when adhering to this rule, at slow speeds it was very difficult to get the machine turning in the desired direction. At higher speeds it was fine.

The steering system uses a Vickers hydraulic pump that supplies pressure to a Char-Lynn steering control valve (called an “orbitrol”). The valve is controlled by the steering wheel. Inputs to the valve send fluid to a hydraulic cylinder which actuates tie rods to both the front and rear turn tables, moving them in opposite directions. (If you turn the wheel left, the front tracks turns left and the rear tracks turns right, and vice versa.)

Jeff told me the current Tucker configuration is different than my 1980 machine, though the differences are not huge. Then and now, Tucker uses Vickers V20P hydraulic pumps. According to the numbers stamped on our pump, it was setup to produce 11 GPM (at 1,200 RPM) and it flows 4 GPM through the priority valve rear cover to the steering system. Pump pressure was originally set at 1,000 PSI by Vickers, though Jeff said Tucker would have changed the pressure to 1,600 PSI, based upon having long tracks with the front blade option. (Note: Snowzilla’s pump configuration is different, as it doesn’t have the factory six-way blade. IIRC, the pump's output volume is 8 GPM.)

The current Tucker production machine of roughly the same size, and with a front blade, uses a 13 GPM pump, 6 GPM out the priority valve and output pressure has been raised to 2,200 PSI. Tucker also installs a dual cross-port hydraulic relief valve in the system as a safeguard to protect against overpressure. The increased priority valve flow will make the steering quicker, and the increased pressure will reduce the steering effort required. Tucker installs the dual cross-port relief valve between the steering control valve and the steering cylinder. The relief valves are made by several manufacturers. I chose a Prince brand unit due to price and availability. (Here’s a link: http://www.princehyd.com/Products/Hydraulic-Valves/Relief/Model-DRV)

It came preset at 2,000 PSI, though Jeff Godard recommended it be set at 2,300 PSI. We tried adjusting the pressure with a hydraulic Porta Power unit, but ours didn’t develop enough pressure. I took the valve to a hydraulic repair company in SLC. They used their test bench and reset the pressures to 2,300 PSI.

The pump itself is assembled with various components to achieve certain parameters. It's relatively easy to change some parts and completely reconfigure the pump. Here's a link to a Vickers publication with excellent exploded view diagrams and information:
http://drc.hyd.com/public/E/eaton/d...es/V20 -11 -12 -22 Parts M-2004-S 1998-03.pdf

On page two, in the upper left, you'll see a diagram of the priority valve rear cover. Increasing the volume from the priority valve is done by increasing the size of the orifice. (Flow volumes for different orifice sizes are listed on page three.) Pressure is increased (or decreased) by changing the number and/or thickness of shims just inside the "363889 plug”. Output volume is changed by changing the ring, as well as the rotor and vanes. You can buy a "cartridge kit" which has the required parts. However you’ll note from the diagram there are different “pin” part numbers. The cartridge kit doesn’t include those, so they must be purchased separately. Rings for higher volumes are thicker than ones for less flow, and the bolts (called screws in the literature) may be longer depending on the ring size changes. Parts from Vickers are obscenely high in price, but there are aftermarket parts available at substantially lower prices. (If I remember correctly, I was quoted almost $400.00 for a cartridge kit from Vickers but I bought an aftermarket one for roughly a hundred bucks.)


Here’s a link to another Vickers publication that has more information and overhaul procedures not contained in the link above:
http://www.eaton.com/ecm/groups/public/@pub/@eaton/@hyd/documents/content/pll_1572.pdf

We removed the pump and disassembled it to make the modifications. The literature in the second link describes priority valve operation in Section E, and makes reference to "orifice O in figure 5", as well as other references to "orifice O". One would think there would be such an item in the diagram, but one would be wrong! If you look on the inside of the priority valve cover, the elusive "orifice O" is the smaller diameter hole in the casting. (See photo below)

IMG_0860.jpg

Working with the priority valve cover, we removed the plug, shims, spring and piston. From the Vickers manual table 3, the orifice size for a 4 GPM flow volume should be .139, and for a flow rate of 6 GPM the orifice should be .170. Surprisingly, our orifice was already at .170! So we reassembled the pump with the new ring, new rotor and vanes and new pins. We were able to use the same bolts to hold the pump assembly together. When we disassembled the pump there were two shims of .016 each. A later pump design has a spring guide between the spring and the shims. I decided to update our pump with the spring guide, and as it was about twice as thick as the shims we removed, we installed the spring guide with no shims as a starting point in the process of shimming the spring to achieve the desired 2,200 PSI. We got lucky as when we installed the pump and checked the pressure it was spot on 2,200!

Speaking of that, you verify the system pressure by turning the steering wheel all the way to a stop and then reading the pressure on a gauge. The gauge is something you’ll have to temporarily install in either of the hydraulic lines from the steering control valve to the steering cylinder.

We installed the dual cross port relief valve by welding two small pieces of flat bar to the Tucker frame, and drilling holes through them for the valve itself to bolt to. You will have to either purchase new hydraulic lines, or have the existing lines modified to add fittings to attach to the relief valve and account for the length of the valve assembly.

After the modifications were complete we took the Tucker out into several feet of fresh Utah powder for testing. The modified steering system worked flawlessly, and I can recommend the upgrade heartily. I will add however, the volumes and pressures discussed above were for a long track machine with a factory blade. If your machine has a different configuration, such as shorter tracks and/or no blade, your requirements are likely different.


 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
Back to the blade portions of the project...

The blade skin, or moldboard, is made from 1/8” steel plate. It would be sheared to size and then bent to our specifications in a press brake. There’s a company literally less than a mile from Scott’s shop that makes snowplows for various state highway departments. They also make cutting edges, and I have previously purchased those, custom made for my applications. I thought they would be a great place to get the moldboard and the cutting edge made - as we don’t have the equipment for either. Unfortunately, it didn’t go according to plan.

I should point out the factory Tucker blade that came on Thundercat was made in three pieces for transport legality. The center section is 8’ wide and there are two bolt-on wing pieces which are 9” wide each, giving an overall width of 9’6”. We’re making Snowzilla’s blade for a customer who does not plan on transporting the machine regularly, so we’re making it one piece that's 9’6”. It will be both stronger and less expensive; the elusive win-win!

Back in early June Scott and I had made a CAD drawing of the blade and its cutting edge (really Scott, I pretty much watched and offered some harassment to “help” him) to the plow company with dimensions for both. I was told I would have it by the end of June. I called toward the end of July (didn’t want to be a pest) and it wasn’t done. Evidently the shop foreman needed a dimension for the depth of the bend across the arc (and I guess he couldn’t take the initiative to contact me). We had specified the radius of bend, but he wanted the depth measurement. Three more weeks pass and I call again. Still not done. I’m promised it will be done that Friday. Scott and I go to pick it up late on Friday afternoon. They can’t find the cutting edge and the blade looks terrible. The specified depth was 2 7/8”, and it should be that depth across the entire blade. But the middle of the blade (lengthwise) was almost flat. What exactly is the point of a blueprint if the dimensions are ignored? I went back inside and said it wouldn’t do. The company’s owner promised they’d correct it immediately, and deliver the blade later in the day.

In fact they did deliver both the blade and the missing cutting edge later that afternoon, and the blade looked pretty good, though we didn’t measure it for accuracy. Shortly after the Labor Day holiday we brought the moldboard into the shop to start our part of constructing the blade by adding various pieces for reinforcement plus “shoes" and other parts for the tilting function. At this point we discovered the re-bent blade may have been re-bent, but it still didn’t match the drawing. Remember that 2 7/8” dimension? Well one end of the blade was correct, but the middle of the blade had a depth of 3 5/8” and the other end was 3 1/2”. Scott thought we might be able to repair it ourselves, but my attitude was they had been given the job, they were months late, their product didn’t match the drawing, and they had been paid. Let them fix it!

A phone call to the owner left me stunned. “The dies on our press brake are worn out and that’s the best we can do. If it won’t work for you, I’ll refund your money for the blade.” Wow! What came to mind was the famous quote about the craftsman blaming his tools. Evaluating where we stood, essentially three months had been wasted. How long would it take to get another firm to produce a moldboard for us? (The cutting edge was perfectly okay.) We decided to spend some time and try and repair the blade. If it worked: Great! If we failed: we were out a few hours of our time.

Scott has a machine called an Ironworker in his shop that’s probably 50 years old, plus or minus. It has a single hydraulic ram and one uses different dies to perform different tasks. Scott has a set of Vee dies that could work like a press brake, but his dies are only 5’ long and the blade was 9’ 6”, so we’d have to make multiple passes, trying to add a little bend. In his shop for repair he had a huge barrel drill bit used to bore a hole about 4’ in diameter in the ground. We could use its substantial weight suspended from the shop’s crane to squash bend out of the moldboard, and the Ironworker to add bend. Maybe not exactly the best tools for the job, but potentially workable.

That’s what we did. Scott ran the Ironworker, while I and a mutual friend of ours, John, moved the moldboard into position for each bend. Before doing any bending we used a soapstone to mark the existing bend points and labeled them from "A" to "O" in different points on the blade. That way John and I could make certain we had the blade positioned correctly for Scott to add a little tweak.

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IMG_1677.jpg

After a few hours of adding bend here, and taking bend out there, we had the blade pretty close. The 2 7/8” dimension was somewhat arbitrary, but the bend radius needed to be fairly consistent along the entire length of the blade, and we achieved that. I hate the phrase “close enough”, but the reality of our repair is that while not perfect, it is close enough, and a whale of a lot better than the so-called "professionals" had done!

Now it was time to cut and weld some steel and make it into a Tucker-worthy blade!

The main structural support is a piece of steel bent into a square C that’s welded lengthwise along the blade, below the center of the blade’s arc. Scott thought it would be more cost effective (meaning equally strong, yet less expensive) to purchase a length of 4” square tubing (same 1/8” wall thickness) and cut off one side. The length of the leg at the top of the C is shorter than the one at the bottom due to the arc. (If we made them the same length, the blade wouldn’t be positioned at the correct angle when attached to the A frame.) Scott decided to use his plasma cutter and took some welding wire and bent a circle to tightly hold the tip of the plasma torch, and then a straight length followed by two 90º bends to position the torch at the correct dimension for the cuts. (Very difficult to explain…look at the photo; it will make sense.) He would then pull his jig and the torch simultaneously to keep the torch in the correct location as he cut the tube. Here are pics.

A dry run showing his wire apparatus.


IMG_1654.jpg

And making a cut.

IMG_1656.jpg

When it came to welding our channel to the blade we bolted the cutting edge to the moldboard first. That would give it some more rigidity. Here’s the channel tack welded to the moldboard. You can see how the channel is positioned below the center of the arc and how the upper leg of the C is appreciably shorter than the bottom leg.

IMG_1678.jpg
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
(Note: I should point out the factory blade that came on Thundercat had a cutting edge that was 4” high and 1/4” thick. The mounting holes were in the center, making the cutting edge reversible. When I got Thundercat that cutting edge had some similarities to a potato chip; meaning it was bent several different ways. While weight is the enemy, sometimes it’s worth it to go with a heavier steel if the additional strength gained is needed. For Snowzilla we thought a stronger cutting edge was desirable, and worth the weight penalty. So our cutting edge is 6” tall and 1/2” thick, with the holes in the center. One can unbolt the cutting edge, flip it end-for end, then bolt it back on and use the other part. (If you’re wondering why the cutting edge has to be flipped end-for-end, the reason is the holes in the cutting edge are punched to make a square hole, and then countersunk for special bolts that resemble carriage bolts. The square hole holds the bolt, and if you turned the cutting edge around rather than flipping it end-for-end, the countersunk side would be toward the blade skin.)

The channel was just the first of many pieces to add. Here are some more in-process photos. Basically all of the reinforcement pieces have been added. What isn’t pictured are the “shoes”, or the bracket and braces that hold the hydraulic cylinder responsible for tilting the blade. The caps on the U shaped channels haven’t been welded on, nor have the guide plates for supporting the blade when it’s tilted left or right. But it’s getting there…

In the center of the blade you can see a 1” diameter bolt protruding. That’s a Grade 8 bolt and the head is welded to the back side of a piece of ships channel. (Most channel steel is structural channel and the short legs, or flanges, are tapered. Ships channel is generally heavier and the flanges don’t taper.) That bolt is the center axis of the side-to-side tilt function. If you look at the main C channel you’ll see that it is skip welded to the blade skin. The reason is twofold, the added strength from a continuous weld is not necessary, and the gaps in the welds allow any water inside to escape.

IMG_1723 2.jpg

IMG_1727 2.jpg

A front view.

IMG_1726.jpg

In this photo we added the vertical bracket for the side to side hydraulic tilt cylinder and its two braces. Our blade skin has more arc than the factory blade and this required us to cope the backside of the vertical rectangular tubing so it would fit flush with the main C channel. Scott then welded the vertical bracket along the coped edges. The hole toward the top is for a 1” diameter pin the hydraulic cylinder will attach to. If you look closely you’ll see the hole is actually a bushing. We drilled a 1 1/2” diameter hole for a short length of 1 1/2” O.D., 1.020 I.D. DOM (drawn over mandrel) tube. The bushing welded in place adds significant reinforcement.


Below and to the left of the tilt bracket is the left side, tilt function guide plate. It was cut from 5/16” steel plate and it’s spaced up from the main C channel 5/8”. That space is for tabs on the pivot assembly to ride in as the blade is tilted. Tucker used flat pieces of steel to gain that spacing and welded everything together. It looks somewhat bulky with all the welds. Scott thought a better way was to use 5/8" diameter solid bar. It was relatively easy to bend it to the correct radius, and when the bar is positioned against the flat steel there are great locations at the intersections for weld beads that are somewhat hidden. It’s just as functional, but a bit better looking - in our opinion.

IMG_1735.jpg

After getting the blade to this point, we moved on to fabricate the pivot assembly. It too is cut from 4” square tube, though the wall thickness is 1/4”. The blade is 9’6” long and is made up of 40 different pieces of steel that all have to be cut to size and welded together. The pivot assembly is just a little over 4’ long and there are 24 pieces of steel in it’s construction. That’s another way of saying fabricating it was time consuming. In this photo it’s not complete, but you can see its general makeup. In this position the blade is not tilted. You can see bushed and reinforced holes in the center. That’s where the A frame attaches with another 1” Grade 8 bolt. The bushed holes toward the two sides are for the two hydraulic angle cylinders to attach. Scott likes to ensure his welds have great penetration, which means lots of heat. With all of the different components and the various welds involved, the pivot assembly developed a very slight arc and Scott used a hydraulic press to gently persuade it back to flat.

IMG_1744.jpg

This photo shows how the guide plates and the pivot assembly's tabs interact. The pivot assembly has a piece of ships channel welded to the top with another bushed hole for the blades 1” Grade 8 bolt, and you can see how that functions as well.

IMG_1745.jpg

My friend in Vermont completed the machining of the A frame's sleeve and the axle clamps for the axle mounted frame. Those arrived and he did his usual beautiful job. I genuinely get pleasure working with such nicely made parts. His philosophy is that one’s work product is a reflection of the person doing it. Nothing leaves his shop unless it’s right. Nothing! Quite the contrast with the company that supplied the blade skin...

(Note: There will likely be a delay before the next update to this thread. The 1642/43 Scott and I re-cabbed showed up from Colorado for repair of the broken rear axle housing. We're going to concentrate on getting that repair done, as well as a few other things they'd like us to tackle.)






 

HankScorpio

Member
You guys are doing great work. Thanks for posting up all the pics. I like that plasma trick with the wire, I will be using it in the future.
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
The changes we've made thus far to Snowzilla have been related to improving the comfort and functionality of the machine, but nothing has been done to improve its performance capabilities. Scott and I firmly believe an automatic transmission is a very worthwhile option/feature in a snowcat. One issue though with the stock Chrysler LA series industrial engines is the available automatic transmission choices. Chrysler offered the Loadflite, which is very similar to their Torqueflite transmission. It is a three-speed, non-overdrive transmission. The Loadflite was offered with short and long tail shaft housings and Tucker chose the short tail shaft style. Those transmissions were not made in big numbers, and are thus very hard to find. In discussions with Tucker factory personnel, they unanimously prefer the other automatic that Tucker offered at that time; the Allison AT545, which is a four-speed, non-overdrive transmission. Those transmissions were made in large numbers and are easily found, and at reasonable prices, too! But there is an issue:

Typically automatic transmissions have a housing, or case, that incorporates the bell housing that bolts to the engine. With medium and heavy-duty truck transmissions, they make the transmission and a separate adapter housing for specific engine applications. For example, whereas General Motors made the Turbo-Hydramatic 400 transmission with separate transmission case configurations for Chevrolet, Pontiac, Buick, Oldsmobile, etc, Allison made the AT545 in a standard configuration with an SAE number 3 bolt pattern and then used an adapter housing with the SAE pattern on the transmission side and a specific shape and bolt pattern on the other side for all manner of different engines. But the problem is the AT545 was not offered as an option by Chrysler for the LA series engines, so Tucker had the adapter housings made for them by a company in Oregon. Finding those adapter housings is extremely difficult. (I have been trying to pry one from redsqwrl’s hands, along with an engine, transmission and perhaps a complete Tucker, but was unsuccessful.)

After basically striking out finding a suitable automatic transmission to replace the stock 5-speed manual, and after considerable thought, research and back-and-forth discussion, it was decided to upgrade Snowzilla to an automatic transmission AND at the same time it would get a "heart transplant” in the form of a new engine. That of course opens up lots of options for transmissions as well as engines. I'll call the new power plant the "mystery motor".

Note, a little history behind the name: Back in 1963 just prior to the Daytona 500, Chevrolet introduced what was called the mystery motor. Junior Johnson won the first qualifying race with one, and Johnny Rutherford won the second qualifying race, also using the mystery motor. There were five cars equipped with that engine and all five blew away the previous year's winning qualifying speed. The mystery motor was a pre-production Chevrolet 427 big block engine. In 1965 Chevrolet introduced the big block - in 396 cubic inches as an option in the Chevelle rated at 375 HP, and midway through the year, in the Corvette, rated at 425 HP (when they simultaneously dropped the 375 HP rated Rochester Fuel injected 327 option). in 1966 the venerable 427 was introduced.

(The mystery motor destined for Snowzilla has nothing in common with the 427 big block, other than my use of the mystery motor name.)

Look what arrived on a pallet. What could it be???
 

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olympicorange

Active member
The changes we've made thus far to Snowzilla have been related to improving the comfort and functionality of the machine, but nothing has been done to improve its performance capabilities. Scott and I firmly believe an automatic transmission is a very worthwhile option/feature in a snowcat. One issue though with the stock Chrysler LA series industrial engines is the available automatic transmission choices. Chrysler offered the Loadflite, which is very similar to their Torqueflite transmission. It is a three-speed, non-overdrive transmission. The Loadflite was offered with short and long tail shaft housings and Tucker chose the short tail shaft style. Those transmissions were not made in big numbers, and are thus very hard to find. In discussions with Tucker factory personnel, they unanimously prefer the other automatic that Tucker offered at that time; the Allison AT545, which is a four-speed, non-overdrive transmission. Those transmissions were made in large numbers and are easily found, and at reasonable prices, too! But there is an issue:

Typically automatic transmissions have a housing, or case, that incorporates the bell housing that bolts to the engine. With medium and heavy-duty truck transmissions, they make the transmission and a separate adapter housing for specific engine applications. For example, whereas General Motors made the Turbo-Hydramatic 400 transmission with separate transmission case configurations for Chevrolet, Pontiac, Buick, Oldsmobile, etc, Allison made the AT545 in a standard configuration with an SAE number 3 bolt pattern and then used an adapter housing with the SAE pattern on the transmission side and a specific shape and bolt pattern on the other side for all manner of different engines. But the problem is the AT545 was not offered as an option by Chrysler for the LA series engines, so Tucker had the adapter housings made for them by a company in Oregon. Finding those adapter housings is extremely difficult. (I have been trying to pry one from redsqwrl’s hands, along with an engine, transmission and perhaps a complete Tucker, but was unsuccessful.)

After basically striking out finding a suitable automatic transmission to replace the stock 5-speed manual, and after considerable thought, research and back-and-forth discussion, it was decided to upgrade Snowzilla to an automatic transmission AND at the same time it would get a "heart transplant” in the form of a new engine. That of course opens up lots of options for transmissions as well as engines. I'll call the new power plant the "mystery motor".

Note, a little history behind the name: Back in 1963 just prior to the Daytona 500, Chevrolet introduced what was called the mystery motor. Junior Johnson won the first qualifying race with one, and Johnny Rutherford won the second qualifying race, also using the mystery motor. There were five cars equipped with that engine and all five blew away the previous year's winning qualifying speed. The mystery motor was a pre-production Chevrolet 427 big block engine. In 1965 Chevrolet introduced the big block - in 396 cubic inches as an option in the Chevelle rated at 375 HP, and midway through the year, in the Corvette, rated at 425 HP (when they simultaneously dropped the 375 HP rated Rochester Fuel injected 327 option). in 1966 the venerable 427 was introduced.

(The mystery motor destined for Snowzilla has nothing in common with the 427 big block, other than my use of the mystery motor name.)

Look what arrived on a pallet. What could it be???

4BTA-3.9L
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
Work on Snowzilla continues. With Thundercat we made the modifications first, then tested them for performance verification. And only then did we disassemble the machine for sandblasting and painting. But the plan with Snowzilla is different. Many of the modifications we’re doing are similar to what we previously did with Thundercat, so proof-of-concept testing isn’t necessary, and we need to get it done for Christmas, 2019. Snowzilla is getting completely repainted (with a color change, no less), but we want to finish all the required welding before it gets sandblasted and painted. Then it will be reassembled with some new components, some modified components and of course some original parts as well. Then once it’s all together we’ll take it out and make sure everything is working properly prior to delivery. Hopefully we’ll have it done... and be waiting for adequate snow to do that testing. But it’s amazing how time flies, and though it’s only the first week of June, I’m mildly concerned about the completion date more than six months away.

We needed to remove the original engine and transmission mounts and get the mystery motor and the transmission (Allison AT545) mounts fabricated and welded to the Tucker frame. That required attaching the engine to the transmission to position them as an assembly in the frame to determine the location for the respective mounts. The Allison's torque converter attaches to the engine’s flex plate with six bolts. The original transmission behind the mystery motor only used three bolts to secure the torque converter. Of course the bolt circle was slightly different as well. These holes need to be in perfect alignment with each other, but the bolt circle must be perfectly concentric with the crankshaft or there will be balance issues. I took the flex plate to an automotive machine shop to make sure it was done right... except they screwed up. To be fair, they owned their mistake, bought a new flex plate and properly drilled the new one. But there was a delay and so progress slips a few days….


Here’s the frame with the engine and transmission removed.

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And with a bunch of parts removed. The original front mount for the engine is still there but the transmission mounts have been removed.

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A close-up of where the front engine mount was. (Bolts were removed for better access to eliminate the original welds.)

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A close-up of where the manual transmission mounts were removed.

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Here’s the frame with the new engine mounts and the original transmission mounts slightly modified, re-positioned and re-welded. Tucker offsets the engine to the left from the frame’s longitudinal center. The only reason we can think of is so there’s room for the hydraulic pump’s 8” diameter pulley. We mount the engine in the center for better side-to-side weight distribution. Due to the different engine and serpentine belt configuration, we have to redesign (re-engineer?) the hydraulic pumps belt drive system. That’s actually quite involved, and then the new specially machined parts are quite expensive as well.

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Pontoon Princess

Cattitute
GOLD Site Supporter
finally someone is going to put a HELLCAT engine in a tucker, how coooooooool....

will sound like it is going 140 mph, that will keep those pesky kristi s in their place

and they all lived happily ever after

:eatdrink::eatdrink::eatdrink:
 
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Blackfoot Tucker

Well-known member
GOLD Site Supporter
So..
.that beast gonna have a "Hemi".....??

I think it's up to wbuffetjr1 to reveal exactly what the mystery motor is. But I will go so far as to say it's not a Hemi... of any generation. The current versions, Generation 3, use the same bellhousing bolt pattern as used on the Chrysler LA series engines (273, 318, 340, and 360 CID) except the top bolt hole in the bellhousing is not used.

We decided to go with an automatic transmission, and more specifically to use the Allison AT545. If we wanted to use a current generation Hemi engine, we would need to find an adapter housing for the Chrysler LA application. I believe only Tucker used that combination and they had the housings made to their specs. I tried, but was unsuccessful, to pry a 360/AT545 combination from redsqwrl's hands (paws?).

But, the mystery motor's bellhousing bolt pattern is fairly commonly used with AT545's, which was a bonus in selecting an engine.
 

Pontoon Princess

Cattitute
GOLD Site Supporter
I think it's up to wbuffetjr1 to reveal exactly what the mystery motor is. But I will go so far as to say it's not a Hemi... of any generation. The current versions, Generation 3, use the same bellhousing bolt pattern as used on the Chrysler LA series engines (273, 318, 340, and 360 CID) except the top bolt hole in the bellhousing is not used.

We decided to go with an automatic transmission, and more specifically to use the Allison AT545. If we wanted to use a current generation Hemi engine, we would need to find an adapter housing for the Chrysler LA application. I believe only Tucker used that combination and they had the housings made to their specs. I tried, but was unsuccessful, to pry a 360/AT545 combination from redsqwrl's hands (paws?).

But, the mystery motor's bellhousing bolt pattern is fairly commonly used with AT545's, which was a bonus in selecting an engine.


so sad, you were our best hope for a hemi...:sad::sad::sad:
 

The Sweet Wbj1

Active member
The engine is a low mileage 6.2 LS out of a Yukon Denali. I think it is something like 420HP and 440 ft/lbs of torque stock. I believe it makes greater than 300 ft/lbs through the entire torque curve. All aluminum block and heads. Listed weight is ~450lbs. I had it for another project that ended up getting sold. After much discussion with Blackfoot the engine headed West. I really wanted more power than the 318 was going to deliver and no matter what engine Snowzilla had I was planning on fuel injection since our cabin is at 10,000'. After looking over systems like the Holley Sniper and the all in cost of one of those combined with the still limited power of the 318, the 6.2 just made more and more sense.
 

Track Addict

Bronze Member
GOLD Site Supporter
Very nice choice. Have had two of those in life. One in a Denali 150K miles and current one in and Escalade under 100K. Both the wife drives.

Only had to do an oil pan gasket on one sometime after 100K miles. Both have been reliable flawless runners with lots of power.

Nice to see the heart beat of America in a Tucker! Congrats
 

The Sweet Wbj1

Active member
Thanks TA! I have never owned a 6.2 in a vehicle personally, but a buddy had one in a Denali. His experience was identical to yours! Hoping it will last forever with such limited usage. Blackfoot is also installing Detroit E-lockers front and rear! I am thinking it will be a BEAST in the snow! Got to live up to the name Snowzilla!
 

redsqwrl

Bronze Member
GOLD Site Supporter
Lockers add a tremendous amount of ability. is the motor a lot lighter or a little lighter?

a pound of aluminum and a pound of feathers weigh the same.
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
Now that the cat’s out of the bag on the mystery motor’s identity,.. By the way, it is considered a Generation IV LS engine and in GM engine parlance it is known as an L94. It was installed in luxury SUVs: namely the Cadillac Escalade and Yukon Denali. At the time, it was the most powerful normally aspirated engine available in a Cadillac. Yes, its sibling the LS3, that was installed in the Corvette at the time, makes more horsepower, but it produces less torque and it's torque curve isn't as flat. While some might think the LS3 would have bragging rights, in the snowcat application having more torque and a flat torque curve makes the L94 the better choice. The L94 makes a whole lot more power than the stock 318, AND having an aluminum block and cylinder heads, it weighs less about 100 lbs less than a cast iron engine of the same size. What’s not to like about that?



The 8.1 was basically the last evolution of the Chevy big block and dimensionally it’s a fairly large engine. The length of the shortest driveshaft we could have made between the transmission and the transfer case determined how far aft the engine and transmission could be installed. But even all the way back, the front of the oil pan (an aluminum casting) conflicted with the front axle/fifth wheel plate assembly. We then had to move all that forward 2”, which also meant lengthening the steering tie rod and the front driveshaft.

When we first positioned Snowzilla’s 6.2 engine and Allison AT545 in the engine bay, it seemed there was tons of room, and we didn’t have to move the front axle/fifth wheel plate/front suspension. While that was a serendipitous discovery, the question was why? We were baffled, took some measurements which confirmed there was over an inch of extra room and didn’t understand why "Tucker had installed the transfer case an inch further aft". Well, it turns out it wasn’t due to a change in transfer case location...

Tucker uses different transfer cases, I think both at customer request and for different applications. The “standard” case in this era is referred to as the 1 5/16” transfer case. (Note: this size is still being used today in some models.) That’s the transfer case specified in the original order sheet for Snowzilla. However, looking at Thundercat’s original order sheet, it came with the heavier-duty 2 1/2” transfer case. That detail explains the extra room. In looking at photos of the other Tucker’s I’ve owned, all except Thundercat had/have the 1 5/16” case.

Part of the disassembly process involves removing the cab floors, the rear seat footwell pieces and the rear seat benches. In so doing we discovered what I’ll call more disappointing workmanship. Sloppy work and poor manufacturing processes are big pet peeves of mine. If you do a job; do it right. And that applies across the board. For example, if you’re soldering copper pipe you wipe the joint. It doesn’t matter if it’s buried in a wall behind sheetrock. Don’t merely “do the job; “define the job” via excellence.

Tucker builds the frame for these machines from various structural steel members that are cut and welded together. Would it REALLY be that much trouble to at least paint these raw steel members with some primer before adding sheetmetal? Not doing so causes rust issues, and when dissimilar metals are in direct contact - galvanic corrosion. I have a lot of respect for much of what Tucker does, but I have contempt for their sloppy workmanship and questionable "quality control”.

Here are some pics.

Note the complete lack of paint on some of the frame members. (Shiny area on cross member is where the back-up alarm brackets were welded before being cut off.)

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Close up of unpainted frame section.

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These two pics are of the rear frame where the footwell’s exterior aluminum skin attaches to the raw steel frame. You can see the needless galvanic corrosion and rust. Note the two vertical frame pieces and the number of fastener holes. Yup, different. NICE attention to detail…NOT

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The fuel system will need to be completely re-plumbed from the gas tank to the engine. The stock canister filter and auxiliary electric pump will be replaced with a spin-on, water separating fuel filter (with drain) and a higher pressure, in-line electric fuel pump as well as a combination filter/pressure regulator downstream from the pump that also has a return-to-tank line that must be plumbed. The various components need to be mounted properly, and we want to determine the optimal locations for each, and then fabricate whatever mounting brackets are required, which will also require some welding. The foot well area in the rear cab on a XX43 Tucker steals a lot of real estate for mounting various components, so the best component positioning and routing of fuel lines isn’t obvious.

Snowzilla gets the benefit of lessons learned on other projects, and it's getting the same modifications to the hydraulic pump and steering system. That means the addition of a dual cross-port relief valve between the orbitrol and the steering cylinder.

Here, some pieces of flat bar have been welded to the Tucker frame. The cross-port relief valve will be bolted to these brackets.

IMG_2258.jpg

Another modification we did to Thundercat that we're doing to Snowzilla is reconfiguring the windshield wiper system for increased swept area and re-positioning the swept area more optimally for the driver and passenger. In general terms we move the left side wiper spindle (the part the wiper arm attaches to) 5” to the right and we move the right side wiper spindle 2 5/8” to the right. Of course this involves drilling new holes in the area below the windshield, welding up the old holes, and modifying the wiper mechanism linkage accordingly. The hard part to this modification was the design work. The modification itself is relatively easy. It’s just some labor, and there are no new parts required! (Note that this modification and the dimensions I listed above are for a 52” wide cab.)

Here’s the modified sheet metal. Look at all the holes in the firewall!

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With the change to an automatic transmission we wanted to add a transmission temperature gauge. As wbuffetjr1 mentioned, Snowzilla is getting Eaton E-Lockers installed in both differentials and it was decided to switch them independently. The exterior lighting system is being seriously upgraded with a plethora of LED lights, and those lights, all require switches. It was then decided to redesign the instrument panel to accommodate all the changes. Scott and I spent some time with his CAD system playing with different alignments and positions for the various dash mounted components. A new aluminum panel was water-jet cut to that design. (I’ll pause for a second and say if you find a good vendor, the water-jet process yields amazing accuracy at a very cost effective price. (It’s Uber cool technology!))

Here’s a pic. Notice the hole with straight sides below and to the right of the largest round hole (for the tachometer). That’s for the ignition switch. The switch has straight sides and if installed in a hole cut accordingly with straight sides, the switch doesn’t rotate if you turn the key in the ignition switch with too much force. Yes, it’s a small detail, but it’s an improvement over the factory round-hole method. We also changed the outside corners from sharp, square corners to rounded ones. There are 14 switch holes for rocker switches, and four of them are spares for future system “growth”. Since this machine is destined for Colorado, maybe some under-cat "mood lighting"?

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The various changes to the electrical system require significant re-wiring, and as pictured above, there are a lot of extraneous holes in the fire wall. Those all get welded closed, and this Tucker’s dash panel, like so many others, has a number of extra holes, eleven to be exact. Scott welded those closed. Incidentally his technique is to use a length of flat brass plate that he clamps directly behind the hole. Using a mIg welder, he slowly fills in the hole (to minimize heat-related distortion) and the steel welding wire won’t attach to the brass. The back side isn’t perfectly flat, but it works reasonably well.

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sno-drifter

Bronze Member
GOLD Site Supporter
Just an observation regarding lockers: Tucker started installing Hy-Torq diffs in the mid '60s. These diffs were made with over running sprag side gears. The differential action was that in a corner, the outside axle would free wheel. The Hy-Torqs were only factory installed in one end of the cat. Our 543 had the triangular grousers with the tapered cleat ends. Our operating conditions were from very deep snowfalls to boiler plate ice. The cat was never operated on paved surfaces so the tapered cleats were as OEM. The purpose of the taper was to prevent side slip on ice, and it works very well. On super hard ice the cleat marks would be about 1/4 inch long. Needles to say, traction was beyond what carburetors of the day would handle and what operators of the day could muster kahonas. The problem with this setup is that in a corner the axle with the locker wanted to go faster than the axle with the open diff. The failure was that the front cross member failed. Fortunately, this was in the era of bolted in vs. welded front trunion cross members. We could ski to the crippled cat with tools, cross member, and jack to repair it. Moral of story, only engage lockers when necessary. Also, an open diff is very useful for side hilling and as a safety to prevent rollover.
 

redsqwrl

Bronze Member
GOLD Site Supporter
Having used ARB and E lockers in wheeled and tracked vehicles. Being in the conversation with track inc folks in regards to locker use in our grooming equipment. Lockers in tuckers are for Getting out of what ever situation you may have gotten into.

My $.02 is about Knowing whether or not you are unlocked.
our experience is with Heavy terra tracked tuckers and operators that doesn't understand common mechanical operations such as differentials.
Lock up in a straight line. unlock in a straight line. don't try to lock while one (wheel or pontoon) is turning and one is not. when you unlock, in addition to the switch saying it is unlocked you need to feel it unlock in the seat of your pants so to say. If you feel bound up ( not in the cheese way) stop and back up a bit. Both style of selectable locker mentioned use substantial force to lock the side gear. both use a simple fairly weak spring to unlock.
we have turn table and track failures due to lockers not being allowed to unlock. It would be easy to blame one operator or the other. but in a day of common sense not being so common, just follow the instructions that come with the device and you will be fine.

I personally like the air based systems.

the air will leak over time. this air vents the differential in a positive manner.
On board air can assist other brand snow cats with repairs ;-)
there are multiple ways to get pressurized are into a locker.
in an Armageddon catastrophic failed seal you can pump grease in it and it will work.

If you fail a coil, slip ring or brush. or your alternator quits. You have to pull the cover off the diff to push it in with a screw driver and It will pop right back out again.

Most of the knuckle head videos on You tube have the break downs and stucks way far away from common sense. stack the deck in your favor and keep the common sense close to the situation.
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
Work continues on Snowzilla…

We removed the windows from the three doors, and the doors themselves, as well as the flat glass in the back of the cab. The firewall's numerous extra holes were all welded up. Then it was time to put the engine and transmission back in Snowzilla so we knew where the powertrain was and could install various components that require welding.

A big portion of the list are the six-way blade’s support frame members. On my first Tucker, and on Thundercat, there are four diagonal support members that were welded to the Tucker’s frame and then are welded at the bottom to a curved, C-shaped channel. (Interestingly, despite being the same model year, they did it a bit differently on the two machines.) A low-friction plastic block attaches to the blade’s axle mounted frame and rides in that C-channel. Before we could think about the support arms, we needed the plastic block and the C-channel.

1980 Tucker 1543 factory blade installation.

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Here’s the factory installation on Thundercat. Why are the rear support
arms different?

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Here’s a pic of Thundercat after we moved the support arms. When we installed the big motor we needed to move the front axle and fifth wheel plate assemblies forward 2” and thus made new support arms. This shows where they attach to the C-channel.

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This is where we attached the two rear support arms. They’re welded to the stout frame crossmember directly in front of the transfer case. This change required moving the brake line and you can see the new stainless steel line secured to the bottom of that crossmember (pardon all the dust).

IMG_2363.jpg

I bought a chunk of low-friction plastic and Scott and I cut it to the correct shape with a radius on the back side to match the curve of the C-channel. It attaches to the axle mounted frame with a Grade 8 bolt, so we needed to drill a hole for the bolt, counterbore the hole for the bolt head, and then cut out the areas for the bolt’s six corners with a chisel.

IMG_2275 2.jpg

The C-channel was more time-consuming. Tucker makes the channel out of 5/16” steel plate on the top and bottom pieces, and 1/4” plate for the back of the C. Scott didn’t have any 5/16” plate on hand but did have 3/8”, so we used that. He used an acetylene torch and a circle burner gizmo to get the radius correct on the top and bottom plates. He then used a hydraulic press to form the arc on the back plate, checking its fitment against the radii of the top and bottom plates, and making adjustments accordingly. Incidentally, to get the two 3/8” plates darn close to identical, he tack welded them together so I could grind them at the same time. After all that was done, he used a mig welder to tack the pieces together and an arc welder and “jet rod” to get the desired penetration for strength. After allowing it to cool, he went back and used 7018 rod to weld the inside corners of the C-channel. We then used a roundover router bit on the plastic block to ease the corners and make room for the C-channels inner corner weld beads.

The C-channel after welding, and prior to clean-up.

IMG_2277 2.jpg

I mentioned above that on Thundercat the four diagonal supports are welded to the frame. That method works, and works well, but accessing the bottom of the transmission to change the filter inside, for example is a PITA. Another issue is you can remove the six-way blade, and the axle mounted frame if you desire, but those support arms and the C-channel are still there. Scott and I discussed the idea of making the support frame bolt-on rather than permanently welded. We suggested this possibility to wbuffetjr1, and he liked the concept. Then we had to turn the concept into reality. Typically in these situations we each come up with our idea, and then discuss them and their respective merits. More often than not we go with Scott’s concept... because it’s better. And that’s what happened…again.

The two rear diagonal braces are welded to the back of the C-channel at the bottom and are welded to two pieces of 1/4” angle at the top. The angle bolts to the Tucker frame crossmember in front of the transfer case with two 1/2” Grade 8 bolts per piece of angle.

Here’s a pic of the rear support arms tack welded to the rear of the C-channel. The big thing that hangs down in front of the arms is the Allison's deep transmission pan (more on that later).

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Here’s a photo of the bolt-on attachment. It’s fastened temporarily, with some hardware Scott had on hand. When Snowzilla is reassembled after painting it will be done with new Grade 8 fasteners. It’s a little hard to see but the support arms are positioned directly in front of some square tube sections that are welded between the two frame crossmembers. Realize the bolts really just hold the angle pieces and support arms in position. They’re directly against the frame crossmember and that’s what bears the brunt of the load, not the bolts themselves. There’s a lot of strength there.

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sno-drifter

Bronze Member
GOLD Site Supporter
And the drive line snakes through there too? Looks tight.

I like the concept of the bolt-in frame. Guess who gets to replace clutches and throw-out bearings here?
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
And the drive line snakes through there too? Looks tight.

I like the concept of the bolt-in frame. Guess who gets to replace clutches and throw-out bearings here?

sno-drifter, you definitely get style points for being so observant. The front driveshaft DOES conflict with the transmission pan. That's the "deep" transmission pan and Allison also offered a shallow pan. I think I previously mentioned (in a post somewhere) that the deep pan is like a kitchen roasting pan and the shallow pan resembles a paint roller tray that tapers. (The shallow pan uses a different transmission filter and requires a different pick-up tube.)

I also agree with your assessment on the framework and the difficulty of removing the transmission for clutch or throwout bearing access. With the factory style welded blade frame I think you need to pull the engine, either separately or with the transmission attached, to get the required access.

My regret is we did Thundercat before Snowzilla, and didn't change the blade framework to a bolt-on style. You learn with each project, and later ones benefit from that added knowledge.
 

Blackfoot Tucker

Well-known member
GOLD Site Supporter
I'm going to address the transmission pan issue now, and then get back to the bolt-on blade support framework modifications.

The AT545 we’re using came with a deep transmission pan, and as sno-drifter suggested, the rear of the deep pan conflicts with the driveshaft between the transfer case and the front axle. Allison does offer a shallow transmission pan, however Allison's pricing is (pick one):

A.) Absurd
B.) Ridiculous
C.) Egregious
D.) Unconscionable
E.) All of the above

(The correct answer is E.)

A new shallow pan from Allison is north of $220 + tax (mind you, it’s only a steel stamping, and it’s not plated with gold, 14K or otherwise). I just can’t pay that and look at myself in the mirror. With Thundercat we surgically modified the deep pan to make it like what we thought a shallow pan looked like (we didn’t have one, or even a picture of one, to copy). It was fairly time consuming to cut it apart and weld it all back together, ensure it sealed properly and make it look good, too.

Here’s a pic of our modified pan.

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And the largest section we cut out.

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Used pans are available from salvage yards, but they know what new ones cost, so they charge accordingly. I searched the Internet high and low for used shallow AT545 pans. One yard in Washington state wanted $170... for a USED pan (YGTBSM!). The yard that had them at the best price (in Arkansas) wanted me to fill out a form that had a whole bunch of personal information. (Really, to buy a used part from a junkyard? Ah...No.)

We also needed a single-neutral valve body and an E-brake assembly for Snowzilla's transmission. More Internet searching revealed a heavy truck salvage yard not too awfully far away. A phone call showed them to be knowledgeable and helpful, and the prices quoted were somewhat reasonable. I drove up there to get the valve body and E-brake components and asked about shallow pans. It turns out they had a few, and the price was better than I had found elsewhere... so I bought two. (Thundercat will get a “real" shallow pan after all.) They have some dents and a bit of rust, so they need some cleanup and TLC, but the cost was hundreds (yes, multiple) less than two new pans from Allison!

Here’s a pic of a Tucker factory installed AT545. Note the shallow pan, and the clearance above the driveshaft. The electrical connection you see (where Allison places the drain) is for a transmission temperature sensor, and I believe that was factory installed as well. The location seems ill-considered; it measures the temperature of the fluid in the pan. That’s after it has left the transmission, circulated through the cooler and then been returned to the pan and mixed with fluid in the pan. Heat is the enemy of an automatic transmission, so having a temperature gauge is certainly worthwhile, but measuring the temperature after the fluid has been through the cooler seems like shutting the gate AFTER the cows got out. It tells you nothing about how hot the fluid is inside the transmission, and that’s where the damage will occur. Our primary concern is how hot the transmission is, not how well the cooler is working. To provide another illustration, where is an engine’s temperature sensor? Is it at the water pump inlet measuring coolant entering the engine from the radiator? No, it’s by the thermostat measuring the temperature of the coolant as it leaves the engine. Same concept...

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