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THIOKOL/LMC/DMC Technical Issues Forum Technical repair issues & questions for Thiokol/DMC/LMC

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Old 11-28-2011, 12:58 AM
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Arrow Thiokol 4T - Rebuild Power Selector (Power Divider)

Thiokol Trackmaster 4T2 - 4T10 (1958? - 1963)

For those of you who don't know - the power selector in the 4T series Thiokol's is the main steering and 2 speed power transfer to the dual rear ends built into these good old cats. So, you have a Low, Neutral and High gearing on each side and use the right or left forward and back which slows down one side and speeds up the other in order to turn, and use both high or both in low gearing for the terrain you are on. They were used only a few years in the 4T series until the 601 series came around and started using the OC-12 and OC-15 rear ends. So you have the engine, the transmission, the power selector and the dual rear ends to drive and turn these babies… I think that in theory the power selector is a great idea because you always have power through a turn instead of braking to make your turn. The main reason I would think that that they moved away from these is that it adds a whole other major component to maintain and is proprietary to Thiokol. Even though they used a lot of normal bearings, etc - the case, some of the gears and shafts were only made for these units. I'm sure some others will chime in on this, but one thing is for sure, after rebuilding this I definitely have a better appreciation and understanding of how they work and when they work right they are a pleasure to drive!

So, on with the rebuild!

Obviously, there are different reasons to have to rebuild a PS, in my case the rear splines of the dual shafts that connect to the drive lines both stripped out in the u-joint end yokes and then the ends of the shafts themselves. I also had oil leakage out of the seals which in turn gunks up the clutches and makes them very inefficient. In my experience make sure you check these shafts as often as possible because they are very difficult and or expensive to replace! It is much cheaper and easier to replace the end yokes or u-joints before they tear up the shafts.

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All that being said - the PS unit itself is not that difficult to pull out, even in a no fancy shop and no fancy tools environment like my cabin where this all took place. So, if you are just replacing clutch plates it could possibly be an afternoon job (after you've done it once or twice).

To start I was able to take out my floor fairly easily and open up everything to work on it. Then unhook the driveshafts (mine had those carrier bearings and a plate they hooked to, which we had to take apart the exhaust to remove the plate) and front yoke plate to the transmission. Then disconnect the shifting linkage on both sides with cotter pins etc.

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Next there are just 4 long bolts that bolt it to the frame - they are free in the slots so we had to have one of us above & one under to get them out - but not hard at all. Then we set up a couple come alongs to lift it out and slide it to the rear door where we could transfer it to my truck and move it the workbench (actually we did some of the work on the tailgate to get the weight down so we could lift it)

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After the unit is out you can then remove the clutches. First remove the pressure plate unit which slides on the splined shaft held on by bolts on the bottom supports and then the pins on the top attached to the shifting actuators (be aware of the bearings on the pressure plate unit - a couple of mine were toast (of course) and one was worn completely to out of round (another nightmare problem I had to deal with) - but not bad to change if in OK shape) Next remove the clutch drums by taking off snap rings, then set screws which can be one on top of another - then hook up the puller to the tapped holes and pull them off - some came off easier than others, but not bad to get off. As you pull them off be sure to gather up the spacers behind them and put in a safe place. The clutch discs all come off easily especially the broken ones and oiled up trashed ones 24 discs (actually 48) - 6 fiber (original asbestos) on each and 6 metal ones which all fit on the spider hubs.

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If all you need is to change the clutches then get the clutch plates if you haven't and reinstall starting with fiber - metal - fiber - metal and so on. Put everything back together in reverse order, drop it back in and drive it away!!!! (so easy - )

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If you have leaky seals (as I did) or noise in the gear box or bad shafts (as I did) then you have to take apart the unit and if you do that you should for sure replace all the bearings while you are in there. I do not have the equipment or expertise to do that part myself so this is where I will defer to the manual and member "spiritsprings" who led the way in talking about his rebuild.

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From the Manual:
The side shafts can be pressed in either direction out of the case. The case can then be split on the center line by removing the caps crews and the housing will come apart. Two of the side gears remain in one half of the case. The power input gears remain in one half of the case. The power input gears and the other two side gears will remain in the other half of the case. Loosen setscrews; Pull spider off gear hub; Press gear hub through bearing; remove caps crews to remove bearing and flange.

Reassembly:
Care should be taken to assure that the proper pre-load is prepared for the taper roller bearing. To accomplish this, perform the steps as follows: With the side gears removed, assemble the case with shaft in place; Tighten cap with screws against shims; Tighten ring with screws against the proper amount of shims to give a slight drag on shaft. (This drag is best selected by noting if the shaft will spin after a sharp twist. This must not be too tight. It should be taken up, however, to remove all slack.) Then reassemble in reverse order of disassembly.

This is my rebuilt unit with the new modified shafts (long, long story - but finally found machinist to modify for different yokes with keyways to hook up to driveshafts)

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About the Gear Oil and Bearings from member "spiritsprings"...
The manual states SAE 80 or 90 hypoid differential lubricant depending on weather. All but two bearings are sealed in the case. The two being the timken tapered bearings on the input shaft. Those timken bearings are not immersed in oil. There are two drain plugs on the back lower split drive case. The lower plug is the drain and the smaller plug directly over the lower is the fill overflow. With the overflow plug removed, pour the oil in the upper fill plug located on the top of the split drive unit, it will be next to the air relief valve. I have heard many ideas on choices of oil, after looking inside of one of these things, I am going with SAE 80, the manual reads to warm up the unit completely before operating. The bearings are sealed so they do not need oil, any overfill or light weight oil can find its way through the main shafts and their bearings into the dry clutch, at that point you too will see first hand how this unit looks inside. Because the timken bearings are above the oil fill line, they will be coated by the slinging of the oil, the thicker the oil the more it will stay on those bearings, which will also cut down on the harmonic hum. That's my story and I am sticking to it.
Mark "spiritsprings"

Our finished unit back in our baby - ready for some real snow!

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AND A VIDEO OF THE FIRST TEST RUN AFTER REBUILD...

http://www.flickr.com/photos/60557827@N04/6373406639/

Parts List and places to pick them up…

CLUTCH PLATES - 24 FIBER AND 24 METAL - (ONLY IF BAD)
John Deere 1010 Tractor
http://www.tpaktopc.net/jd420jd440jd1010strcltch.htm

I WILL TRY TO GET THE BEARINGS PARTS LIST AND ADD IT...

COMPLETE MANUAL FOR Thiokol Trackmaster 4T2 - 4T10 Snowcats
(Has all drawings parts and info about this whole process)
http://dl.dropbox.com/u/26442044/4T10_Full_Manual.pdf
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  #2  
Old 11-28-2011, 01:37 AM
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Default Re: Thiokol 4T - Rebuild Power Selector (Power Divider)

What a fantastic write-up Shopman! Videos are fantastic too! You've found the keys to the gold treasure of the 4T and per your write-up, I agree with your comments on the differences & evolution of the 4T/PD to 601/OC15. At the end of the day, the OC15 being built like a brick $hit-house would have given better reliability/simplicity but at the same time maintenance of it wasn't exactly a piece of cake given weight, access, etc... Not like the PD is a featherweight by any means but it can be extracted faster/easier and a person doesn't have to muck with the axles/sprockets like they do on the OC15.

Another nice advantage of the PD is that you simply click it and let it turn. No need to apply major forces to steer. Granted, when properly steering the 601 it should be in quick pulls so that is also a different experience where the 4T will turn smoothly throughout a curve the 601 (again, when *properly* steered) would do it through a series of pulls & straight lines. Not essential...a person could simply pull lightly and hold to get a smooth turn but not as designed/ideal for diff wear.

Anyway, great write-up and videos! Rep points due!

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Old 11-28-2011, 11:44 AM
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Default Re: Thiokol 4T - Rebuild Power Selector (Power Divider)

Thanks Mainer! That means a lot coming from the 4T Expert... although I am catching up only because of the cat I ended up with...

Since I spent most of my summer working on it one way or another I thought we should post something detailed for others so we can keep the 4T's alive for ever!

The real bonus is that now it drives completely different - Like New! I had figured out how to drive it the way it was but had to use 2 hands sometimes to pull the levers - now it is truly fingertip steering...

I have done some other work on it - still finding leftover "Pig" problems - but this was the "biggie". I will try to get my other work posted to my rebuild thread soon now - I have a few other people to thank and show how it is coming along.

But now -
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Old 11-29-2011, 02:16 AM
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Default Re: Thiokol 4T - Rebuild Power Selector (Power Divider)

What a great posting! I have a 59 Thiokol 4VL, my power divider looks different from yours. Here are a couple of picutures. With your postings and the manual I might be able to work on mind. My cat still steers but not evenly. Any ideas? Maybe Mainer can weight in on this problem. Has anyone worked on this type of power divider? Again, awesome job on this posting of your rebuild. Pictures and video! Yahoo!
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Old 11-29-2011, 01:06 PM
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Default Re: Thiokol 4T - Rebuild Power Selector (Power Divider)

Thanks nikadog!

Yours is definitely NOT a power selector - that's why I put the ? on the year because I don't know exactly what years the PS's were used in these cats. My manual is for 1962 - which is what mine is.

Hopefully someone else will chime in who knows when and exactly what type of rear end yours is... looks kind of like a tractor-like braking predecessor to the OC12 or??
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Old 12-12-2011, 11:56 PM
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Default Re: Thiokol 4T - Rebuild Power Selector (Power Divider)

So, had some questions about adjusting the Power Selector and made a little drawing for myself a while back... made it a little more readable and ta da...

HOW TO ADJUST A POWER SELECTOR FOR ALL TO KNOW

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PS_Adjustment.pdf

It's still kind of an art form though, so use it as a base - depends on clutch condition and other unknown problems...
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Old 12-13-2011, 12:00 PM
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Default Re: Thiokol 4T - Rebuild Power Selector (Power Divider)

Quote:
Originally Posted by nikadog View Post
What a great posting! I have a 59 Thiokol 4VL, my power divider looks different from yours. Here are a couple of picutures. With your postings and the manual I might be able to work on mind. My cat still steers but not evenly. Any ideas? Maybe Mainer can weight in on this problem. Has anyone worked on this type of power divider? Again, awesome job on this posting of your rebuild. Pictures and video! Yahoo!
Wish I could but I haven't opened up the V's yet so it's a nice mystery box at this point. Then there's the predecessor to these! and before that... the wheel... with a track on it. But yea, these were from 59-62.

But certainly a derivative of the initial brake steer designs (patents were granted and then purchased by Thiokol on these so I don't *believe* they were 100% direct licensing from pre-existing designs) yet we know there was so much sharing between the old tractors/dozers with these machines. I'll keep sniffing around for materials.... other than that... a good summer project to disassemble and inventory, etc...

But to your point about your machine not steering evenly... it may be as simple as linkage adjustment or replacement of brake lining material. If it's not running evenly (rather than steering) then that's a different story on tracks/running gear but like you said, if it's steering then into the black box (rather orange) you may choose to go... probably off-season preferably.

It's been fantastic to see the forum develop such a great following of the Thiokol machines and getting more documentation/understanding each day on these classics. Great to see them resurrected and not bastardized (different than improved)!
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Old 12-21-2015, 03:09 AM
m37dodge m37dodge is offline
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Default Re: Thiokol 4T - Rebuild Power Selector (Power Divider)

Did you have any luck finding anything out about this differential??
I have the same style in my 4VL / SN PBT-3 .
I think you have #4
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