afternoon everyone. a little bit about myself, purchased a 1980 1544 tucker last fall. it has a mopar 318 industrial hooked to a 5-speed transmission. after doing some research and calling Tucker. I found out that this machine could have been spec'd with an automatic. in fact from an old build sheet from Tucker they hooked it to an Allison 540. my question is does anyone know what is needed to do this conversion???? the reason this is so important to me is I have to drive with hand controls - my feet/hands don't work very well caused from a medical condition. by doing the conversion would allow me to drive my own machine and not have to take someone who have the use of their feet. if someone has done a complete restoration and cataloged everything, I could then start my search in finding everything to have someone do the conversion. starting out I need an Allison 540, maybe an adapter to hook Allison to engine, flexplate to bolt Allison T/C. from the build sheet I have cooler number, morse control number as well as length of shifting cable. again, thanks for letting me join and hopefully someone can assist
First, let me say that I admire your determination to do what you want - even if hand controls are required. My brother-in-law is a paraplegic, and I respect the hell out of him. He accepts no limitations and he never complains. He just perseveres until he succeeds. Yes, he's pretty cantankerous, but he sets an example few of us live up to, at least in my opinion. Forrest Gump famously said "Life is like a box of chocolates...". I think life is like a card game, and as you go through life you're dealt different hands. Some are good, and some aren't. You have to play the cards you're dealt. Some people fold early (give up), while others do the best they can with the hand they have. Those are the people I admire.
Tucker offered two different automatic transmission options; the Chrysler Loadflite (a version of the 727 Torqueflite) and the Allison AT545. The Loadflite was available in either a long or short tailshaft configuration and Tucker used the short version. The short versions are VERY difficult to find. The Loadflite is a three speed, non-overdrive transmission.
The Allison AT545 (or 540 or 542) is a four speed, non-overdrive transmission most commonly found in medium duty trucks. They are plentiful and can be found at reasonable prices, too. BUT (there's always a but...), there are some nuances to be aware of.
The biggest hurdle, and already mentioned, is finding an adapter housing to mate the AT545 to the 318. The Chrysler 273, 318, 340 and 360 engines are all in the LA engine family and I'm almost positive the AT545 (and its siblings) were never offered by Chrysler with that transmission as an option. So finding that adapter housing is extremely difficult.
The transmissions were available with different valve bodies; either a double-neutral or a single-neutral. Some explanation is in order:
Whereas automatic transmissions in cars, SUVs, and pickup trucks have a "park" position in the shifter that engages a parking pawl in the transmission, the AT545 does not. The double-neutral has a shift pattern of N, R, N, D, 3-2, and 1. The first N is designed to be utilized with a parking brake mechanism that engages in the N position. But as the shifter has a limited number of positions, you give up the ability to limit the transmission to second gear. The single neutral pattern is R, N, D, 3, 2, and 1. You need to manually set the parking brake in the N position. But you have more control over what gear the transmission stays in. I have a 1986 1544 with a 360 and an AT545, and Tucker used the single-neutral valve body. In our Thundercat project we chose an AT545, and also chose a single-neutral valve body for it. I think it works well. The transmission shifter you purchase should match the configuration of the valve body. Tucker may have used Morse shifters in 1980. But there are other brands. Both my 1544 and Thundercat use Felsted brand shifters. They're made by a company called Orscheln. Be aware Orscheln offers a lot of options and you want to get a shifter that's configured correctly for your application. (Felsted/Orscheln shifters can often be found on eBay without too much trouble.) It's likely you'll have to get a cable between the shifter and the transmission made up to the length you specify, but it's a relatively minor issue.
Allison offered a deep transmission pan and a shallow pan. The deep ones are more plentiful, by far, in my experience. If you don't have a front blade you may be able to use a deep pan, I'm honestly not sure (Tucker used the shallow pan on the 1544 I have, and it doesn't have a blade). The deep pan resembles a roasting pan and it's five inches deep. The shallow pan looks like a paint roller tray, and the deep end is four inches deep. The shallow pan uses a different filter and a different pipe between the transmission and the filter. All of this stuff is available new from Allison, but be prepared to be shocked when they tell you what the parts cost. When it come to outrageous pricing, pharmaceutical companies get all the bad press, but Allison is every bit as egregious!
AT545s were quite often equipped with a parking brake drum just in front of the output yoke, and this too is something you want. The mechanism is actuated by the same parking brake lever in the cab as your five-speed uses.
With your existing engine and transmission, the bell housing has some ears cast into it that are used as mounts. There's a single bolt in the front of the engine and the two ears on the bell housing. The transmission basically hangs off the bell housing with no additional support.
The AT545 has locations on both sides for brackets to bolt on. With our Thundercat project we cut off the mounts Tucker welded to the frame for the original five-speed mounting setup, and relocated them to use with the brackets for the Allison. Tucker used a different setup when they installed the Allison in my 1986 1544. Pictures are useful:
Here's my snowcat buddy Scott cutting off the stock Tucker frame mounts used for the bell housing ears.
Here's a photo of the engine and transmission. You can see the bolt-on brackets just behind the wide lifting strap. Note also the parking brake drum and mechanism.
And here's a pic of the installed transmission mount.
There are some relatively minor tasks involved like re-configuring the brake and clutch pedal assembly without the clutch pedal, and locating the new shifter assembly. There are some wiring issues you'll have to address with the neutral safety switch for starting, and the reverse gear switch for backup lights / backup alarm. You'll also need to have your existing driveshaft shortened, or a new one made, and you'll have to address the transmission's modulator.
This is not an easy and fast conversion. It's a lot of work, and if you have it done by others, you'll want someone with the knowledge, skill and time to do it, and do it right. My snowcat buddy and I agree that an automatic transmission in a snowcat is a very desirable feature, and we think it adds several thousand dollars to the resale value of a machine. But to do the conversion, or have the conversion done by someone else, I'm not sure you'll get all your money back out when you sell the machine. On the other hand, it's not like there are a ton of nice, used Tuckers with automatic transmissions to choose from.
My sincerest best wishes for your project. I'll do my best to answer any questions you have.