M35A3 Transmission type?

simp5782 said:

I received a call from a guy that bought a transmission thru a fellow SS member about 6 months ago for an A3. I just found the transmission and took care of the shipping. I inspected the transmission and the tag on the transmission showed to be a 1545. The broken transmission was not out so could not be compared side by side but seemed to be identical. I was not involved in the R&R process. Apparently the old torque converter had extended bolt holes on it that sat way out towards the flywheel. The replacement one did not. I have heard it was swapped in and out of the truck 4x and after even making spacers to get the torque converter to reach out. Apparently the transmission would not work. the culprit found was a cracked sleeve on the front pump. I believe may have been caused by them binding it up trying to force it in or something. but who knows with the can engine and transmissions.

The guy tells me that his 99yr model has a totally different transmission that any other year model. I have not heard or seen anything on this. I did search some threads but most transmission threads are on the A2s or about A3 fluid. I was also told you are suppose to look military parts up by years rather than variant of the truck. So I shook my head on that.

My question is this. is the 99yr model a different transmission? Or is it a 545 over a 1545? but isn't a 1545 just a 545 with lockup? I called CSMDavis on this and he did not know of a transmission change. Is it possible uncle sam just swapped something in or maybe a prototype? I could have swore I checked the tag on the transmission and it said 1545 on it on the burnt up one.

I don't like being accused of ripping someone off when all I did was find someone the part they were looking for. I just am curious to learn something new.

In reference. This A3 is the bobbed crew cab that was sold by C&C a few years ago.

Pictures are the front pump from each transmission. The one on the right is what came out of the one in the can the 1545 tag on it.

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rustystud said:

The pump assembly on the right is for a "non-lockup" transmission (ie: 540 model) . The left one is for the lockup model 1545 . The longer "Stator" shaft supports the lockup clutch assembly.

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tobyS said:

Yep...the diameter of the lock-up TC, the pump side, is larger too. Everything but 2 seals (the TC) on a 545 rebuild kit works for the 1545 (except valve body is different).

Obviously a committee made the decision to make the A3 the only vehicle in the world that has a locking TC on a 545...an extremely popular tranny otherwise. Personally, I'm not sure I'd prefer a 1545 over a 545 unless I planned to be on the road all the time.

I have a spare 1545 (r and 4th out)...but not replaced with the rebuilt one yet.

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rustystud said:

Your direct clutch assembly is bad. Rev/4th gear is the tell. To bad I'm not closer. We could have that unit up and running in no time. I always loved rebuilding the Pre-electronic Allison's . They all had such great internal designs with easy valve adjustments.

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glcaines said:

I personally think that the use of motor oil may help to shorten the life of these transmissions. After I purged the motor oil from my A3 and switched to Dexron 3, my transmission shifts much more smoothly and much faster than with the motor oil.

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tobyS said:

glcaines...Oil, I definitely agree. As an A3 owner, do you think the 545, without the locking TC, would be a suitable replacement??...they are readily available and if your not on the highway all the time, would seem fine. I have one in an International bus behind a 345 gas engine I may recover for someone that wants a lesser expensive alternative to the 1545. The engine spun a rod bearing and I did an in engine replacement of the bearing (hand filing the journal) to see if the tranny worked and what else might be wrong. The tranny worked properly. I didn't run it long enough to screw up the new rod bearing and now it's set for about 12 years or so. Maybe Rustystud can tell me if there is a difference in 545's that I should be aware of.

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tobyS said:

I bought the truck after the owner bought a used tranny ("guaranteed" for what that is worth) and had the same r/4th issue. He disassembled the original and threw it all in a box after he saw the r/4th clutch pack and that it was hot enough to melt the piston. It looked like trash in a box in the bed. On closer inspection, knowing the truck had low miles, all the bearings and gears were in great shape, just had aluminum particles (with dirt and grit) everywhere.

I have a fellow near me with Allison certification so relied on his experience. I was surprised that the piston was readily available and so were the frictions and steels, being same as the 545 and maybe the TH400. The tranny in my photo is the rebuilt one, ready to go in now that the pump is mated to it.

I had as much $$ in the rebuild as I could find a military rebuild for, but after having a TC case in my 817 that was clearly not set up correctly (but new), my trust in military "rebuild" or NIB, was not high confidence. I know exactly what is in (and on) this one.

And by the way, FYI...Dacco is the only place that will rebuild the locking torque converter. I'll be extra careful with the heavy TC, now that I know what happens when it's not supported.

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tobyS said:

I'm happy to report that Joe (Scar 59)'s Allison 1545 is rebuilt and ready for service by my friend Matt. Matt has not had it since 2017, when Joe was having problems in this thread, however.

I'm bringing it up to share what Rusty and Matt have helped me to locate parts that are used in another GM product, the 4L80, that have high performance "direct" clutches available that fit the 1545 weak link, the fourth/reverse. They increase the area by 40% (2 additional frictions). The bonded piston is much superior to the aluminum with seals, I read it puts 25% more force on the clutch too. My first rebuild and Joe's both have the OEM piston, and the new style seal, so they are ready to go but the next is getting the improved high performance clutch pack.

I'm going to be removing the 1545 (broken) in my truck and replacing with the (earlier) rebuilt one, so will have a spare tranny to put the high performance clutch pack into.

Also, a man responded to my "wanted" parts ad for a 1545 core. He sent photo's of one and all. Things that appear too good to be true....usually aren't. It was a scam. I almost took the bait. Glad I didn't and that I spotted the post of other people getting scammed.

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