M35a2 automatic transmission swap?

[DB556]

Well I couldn't get the guy to part with the MD3060, but did find a allison 2400 on marketplace with shifter and computer that was behind a 24valve 5.9 in a freight liner. So now I'm reading through 40 pages of wiring info on 4btswaps on how to make it run behind a 12v. Wiring. Is. So. Much. Fun...

 

[Sgt Jiggins]

Wiring. Is. So. Much. Fun...

Which is exactly why I was looking at the MT643 as a possible replacement for the 1/545 - I don't want to go electric on a truck that is otherwise purely mechanical. But that's just my position. I know there are people out there who wouldn't have done other 'mods' to their trucks that I've done to mine.

Maybe something will pop out if this goes full circle again...

 

[DB556]

And I when to pick up the allison, and found a huge crack in the case and a crushed oil pan... I just cant win, the guy must have dropped it.
Back to the drawing board maybe the MT643 and a Eaton 3-A-65 or maybe one of the other ones they make.

https://www.eaton.com/EN/rr/ProductsServices/ProductsbyCategory/Transmissions/PCT_486870

 

[DB556]

I've got a line on a MT643 with PTO and hydraulic pump from behind a 12v 5.9, So I'll see about grabbing that this weekend.

Now I cant seem to find any overdrive auxiliary transmissions, so I had funny idea on the overdrive transfer case idead

Could the gears be reordered in a T136? swapped from a 1.96:1 to a 1:1.96? which would be a 0.52 overdrive? Its a very high steep overdrive but?

 

[DB556]

On a cursory look at TM902520-246-34 the gear shaft diameters for the high and low both appear to have the same bore 2.3765" and key way size or .499" so swapping the gears around might just work

 

[Sgt Jiggins]

@rustystud or @tobyS you have anything for this thread?

 

[DB556]

Well I got the MT643, it came with a PTO and hydraulic pump which will work well with my crane, The transmission probably weighs almost half as much as the volkswagen I put it in

Now to get is cleaned up and put on a shelf for a while. To give me a chance to find another T136 to experiment with or possibly a NP203 or NP205 that I can do the same high low swap on Though I've heard of them just being run backwards. and put it before the T136 in place of the jack shaft, since I am going to need to move the transfer case back atleast a 12" anyway

 

[Sgt Jiggins]

I'm "watching" this thread for sure.

From what I've heard, you're going to have to trim down the ears on the housing on the MT643 a bit to clear the frame rails. But it should just bolt right up - it's the same 6 bolt pattern as the AT(1)545 from what Jason at Darpco in Charlotte told me. You're also going to have to run larger coolant lines up to the radiator. And a different cooler. But as you're willing to do the rest of that swapping (transfer cases) you'll be just fine with that bit.

When I get to doing this, I'm going to be talking with the guys at Darpco in Charlotte. They have the parts ready to go.

PS. it's worth noting that the Canadian variant of the M35A3 came with a MT643. Granted, it's behind a different engine. But. It can fit and it does work.

 

[tobyS]

I don't have anything to add, but if not gaining OD, would stay with the 545, due to weight and size. Axle ratio is what Iwant to change. I would use the 4L80E direct clutch high performance in it.

 

[Sgt Jiggins]

I don't have anything to add, but if not gaining OD, would stay with the 545, due to weight and size. Axle ratio is what Iwant to change. I would use the 4L80E direct clutch high performance in it.

The 2 thing I can add to that line of discussion (because I otherwise agree) is that the MT643 includes the torque lockups in 3rd&4th that the 1545 did (and the 545 does not). That aids in braking. And the 545 is right at the very peak of it's curve in terms of torque/hp. The MT643 came out of heavier trucks (5 tons?), isn't peaked out, and on the down side: is heavier. The weight isn't killer - the Canadians did it... but that's just my opinion. TobyS is the guru here.

 

[tobyS]

The Canadian example is a great argument since the engine is changing too in the OP post and putting the hp, rpm and torque up. I had multifuel in mind. Still, axle gears seem to be the place to bring the deuce to safe highway, not turning driveshaft faster.

I like the challenge that the 1545 has presented on a tight budget. If I had some extra cash, I would buy Derricks 1545 and start a trade in of them.

 

[DB556]

Well I was cleaning up the MT643 and got out my skid steer to load it onto the bed of the duece to get it out of the way, and the chain I was using to lift it decided to snap, dropped it almost 5ft and crushed the oil pan just my day....

Did find a divorced for NP205 that I'll try to make a jackshaft/overdrive out of, to keep the oil temp down I'm thinking of using the front drive shaft output since where not using it to drive a oil pump of some link and a oil cooler behind the cab or along the frame.

 

[Sgt Jiggins]

Sorry about the carnage, but I'm curious how this goes... definitely post pics as you go.

 

[cattlerepairman]

DB556, I can only imagine the frustration. At least you did not break the case as it was on the other Allison you had looked at earlier. If it's just the oil pan, it's not too bad of a Murphy tax to pay. Good luck!

Sent from my SM-G950W using Tapatalk

 

[DB556]

Well I don't know if there was any damage to the valve body on the MT643, guess I'll find out once I drop the pan.
Though trying to find a new pan as been a task. guess I'll try to hammer the pan out since I've found only one place that has it in stock and its $400.

 

[Sgt Jiggins]

Well I don't know if there was any damage to the valve body on the MT643, guess I'll find out once I drop the pan.
Though trying to find a new pan as been a task. guess I'll try to hammer the pan out since I've found only one place that has it in stock and its $400.

Have you tried darpco in Charlotte? They're decent to work with. Other option might be a junkyard...

 

[gringeltaube]

.... so swapping the gears around might just work

That has been studied already and is not so easy...
At the very least you would need a new T25 gear, fitted to the output shaft.

 

[DB556]

That has been studied already and is not so easy...
At the very least you would need a new T25 gear, fitted to the output shaft.

View attachment 808845

Thanks for the info! I'm going to try the NP205 backwards first, since its a bit easier to find np205s vs T136s

 

[Jeepsinker]

I was considering doing an automatic behind the 5.9 in mine, but it was cost prohibitive at the time. The Allison 1000/2000 series can be had with an SAE2 or SAE3 bellhousing, and parts are available to bolt them right up the the Cummins. In fact, my engine had one behind it when I bought it, but I couldn't afford to buy both at the time. There are standalone wiring harness and controller kits available to run it behind a manual engine and the kit cost is around $1200. The 2wd Allison is also only marginally longer than the Spicer 3053A, and while I didn't go so far as to measure it, I think it could be installed without moving the transfer case back. You also get the benefit of a six speed automatic here if you get a 2006 or later transmission.

The NP205 will probably hold up especially since your truck is bobbed, and there is a boatload of aftermarket support and upgrade parts available for it, including input and output flanges that will bolt right to your driveshafts, heavier mainshafts, etc. This is not a bad choice, and I have considered it myself.
You will lose the park brake though, so be sure that the transmission you get either has a park pawl in it, or have one installed. Many of these transmissions, especially those from medium duty applications that come with SAE bellhousings won't have a park pawl in them, so if you use the 205 you'll have no way to keep the truck stationary when parked.

It is also worth noting that I haven't broken my 3053 yet, and even the Waterloo 5th gears are holding up fine. I figured if I was going to break it, I would have already. I have been in Korea since late March, but I put quite a few miles on it before I left and I'm not exactly easy on it.

 

[Sgt Jiggins]

I was considering doing an automatic behind the 5.9 in mine, but it was cost prohibitive at the time. The Allison 1000/2000 series can be had with an SAE2 or SAE3 bellhousing, and parts are available to bolt them right up the the Cummins. In fact, my engine had one behind it when I bought it, but I couldn't afford to buy both at the time. There are standalone wiring harness and controller kits available to run it behind a manual engine and the kit cost is around $1200. The 2wd Allison is also only marginally longer than the Spicer 3053A, and while I didn't go so far as to measure it, I think it could be installed without moving the transfer case back. You also get the benefit of a six speed automatic here if you get a 2006 or later transmission.

I had been operating with the idea of avoiding the newer electronic transmissions (well, anything electronic given that the rest of the truck is mech-only), but it sounds like that will be the way I go when the current one no longer serves. There's no need for anything other than the barebones 2wd ones on an M35A3 given the divorced transfer case and the on-engine pumps for everything else. Awesome, thanks!!