The Stovebolt Site Forums The Parking Lot Big Bolts Allison automatic - PTO

Does anyone know if Allison made an auto trans with a pto? Supposedly, a friend of a friend has one and it came out of an 80's Chevy medium duty dump. All the medium duty dumps with the Allisons that I have seen, all ran with central hydro units.

Yes, they did and do. Not all of them have the gear inside for a PTO, but it was and is an option.

Grigg

AT540 was a popular trans model in the 80's. Probably still made. The PTO's of that era were available from Chelsea and Muncie which were rebranded Chelsea's until the mid 80's or so.

I have installed a bunch of them but have never run into one that did not have a drive gear in it as Grigg suggests. They are expensive and required a lubrication line to force the lube into them as the PTO opening was very high up on the side above the fluid level. To operate one must place the transmission in gear to stop the drive parts, then engage the PTO and then return the transmission to neutral (N)to start he PTO.

When you say central hydraulics I must assume you mean a crank driven PTO/pump, the way a mixer or plow truck is powered.? Regular dumps have no other hydraulic requirements than the hoist so transmission powered pumps are ther norm.

We run alot of trucks with Allisons, but none with pto's. We have no need for it in beverage trucks. Several of the trucks that we have sold with the MT643 have been turned into dump trucks and winch trucks. I would assume these had the gear, as they said all they had to do was remove the cover and bolt on the pto unit.

Dave's right as usual,
I checked the AT 540, 543, 545 manual I have here and they all should have PTO provisions. Same goes for MT 640, 643, 650, and 653 according to the service manual

I also checked the sales literature I have for the new electronic Allison's, and a model 3,000 or 4,000 was/is available with a PTO delete option.

The transmission in question should be an old style, and therefore would (should) have the PTO option standard.

Grigg

Thought I might ad that if the allison tranny is in a School bus, chances are it won't have the pto drive gear.

I bought a 643 out of a wrecked Ford school bus about 25 years ago. I remember when I called Stewart and Stevenson about a PTO for a hydraulic 5th wheel, they never asked me if it had a drive gear. I just put the PTO on and shimmed it like any other PTO. I now have a yard truck with a 6v53 and an Allison of some sort. It also has a pto driven hydraulic pump.

I've been working on them for 28 years here in North Carolina, & only found a pto drive gear in one AT 545. They weren't spec'd, for North Carolina.

My 1976 GMC wrecker with an AT540 has a PTO that runs the hydraulic pump for the wrecker. I replaced the transmission with a used one from an old school bus that had been rebuilt, and it has the gear for the PTO as well.
Jim

Thanks for the insight. The reason I was asking is I was thinking of putting it in my 41'G506 that has the factory dump. I was originally going to use a SM 465 so that I could run the PTO but then this option was brought to my attention. This way i wouldn't have to mess with setting up a clutch. What do you guys think? What kind of size difference am i dealing with?

And Dave, yes - I was refering to a pump driven off the motor that runs the dump/speader/plow controled by a valve body.

So can I unbolt the PTO set up from the SM465 and bolt that right to a AT540?

WHOA...I didn't indicate that they were interchangeable. They may be but please don't assume that. There are tremendous differences in PTO's across the board and it isn't just whether they will bolt up and engage either. I once had a customer who broke the entire side out of a Fuller RR because his PTO had a higher torque rating than the transmission did so guess which one failed...? This is always a problem with twin countershaft transmissions but back to the Allison.

First of all a PTO for medium duty truck with a CH465 is likely but not necessarily to be a single gear unit. There are no single gear units that fit older Allisons. Next is the issue with lubrication that I originally pointed out. Single gears have no such provision. Next would be the torque issue. Lastly is the fact that even if it did fit it wouldn't protrude far enough away from the tranny to attach anything. All the AT PTO's are double gear. That means that the driven gear inside the PTO is always running and the output shaft gear engages off of it. A single gear PTO is a sliding gear that is engaged on the transmission only as needed.


Send me your model numbers and I'll track it down for you and tell you what you need, OK?

Thanks for the schooling. Obviously, I have little experience with the bigger stuff and am not ready for my ASE Medium duty truck certification test j/k.

I'll try to get some numbers from the fellow tonite. What's your thoughts on the size of this unit? (Compared to a SM465)Is this feesible to fit into a 1.5 ton?

Based on what you've said, I'm thinking unless this unit comes with the PTO setup, I might be better off sticking with what have instead of getting into a big parts hunt.

Personally I doubt if it would fit. They are large and long transmissions and quite heavy too. It would require a great deal of work to make it fit and might even require lifting the cab off the frame to get it in (if at all)

The only GM trucks of that era that I've seen Allisons in were military.

A little bit OT but just as a side note, F*^d A/T's in F350-550's also have to be optioned with a drive gear for the PTO. A lot of folks have found that out the hard way. New tranny in 10' so not sure about the new ones.

After a little bit of internet research - I found a 545 on Ebay for $400. It had the PTO provision and had the dimensions as being 27" long. That doesn't seem much bigger than the 465 would be. Am I wrong? And Dave, what do you think the PTO adapter and set up would run me?

The Allison is reasonably large.
The manual transmission hangs down from center line a lot, while the Allison is bulky all around center line, and some more below.

Unless you really have to have an automatic I would stick (pun intended) with the manual.
Your indecision on what transmission to use tells me the trouble, work, and expense to swap to the Allison is not worth the effort.

Also consider how the transmission ataches to the engine.
What engine do you have, and what is the bolt pattern on it and on the transmission?
The Allison I'm guessing has an SAE #3 bell housing (round with 12 bolts), It would be easier if your engine already has the SAE adapter or flywheel housing on it. If you already do then still may need to find the right flex plate and torque converter too.

Grigg

The fellow claimed the trans was behind a gas tall deck, so I assumed it would bolt up to my small block. However, Grigg you make a good point - I would need to find the right flexplate, because I think the tall decks are externally balanced like the other BBC's. The whole reason I was chasing down this idea was to cut out the effort of setting up a clutch and ease of drivability.

So after the advice given here, I think I should just stick with the 465. It sounds like i'll be chasing my tail trying to find all the parts to make this work. I hate chasing parts around that I end up paying top dollar for.

Thanks for the advice.

I don't have the time right now it is time to go to work but I will be back!!!
I am putting an Alison 540 in my 56 Chevy two ton dump truck with a 496 big block stroker feel free to look though my webshots page and get some ideas and I will return in a day or two to answer questions

Grant, Looks like your into cutting up trucks like me.

So what was your 540 out of, and what mods did you have to make to fit it? Are you running the PTO off the 540?

I am not sure what this 540 is out of I found it on Craig’s List. I do know that it came from a Chevy powered medium duty truck or bus as it came with the SAE-2 to Chevy bell housing adapter and it dose have a PTO gear behind the cover. This transmission mounts much like the originals from the sides of the bell housing it even came with mounts that bolt to the side of the transmission and bring the mounting point down to the stock mounts on the cross member. The clearance problems that I have run in to are at the back of the bell housing to mid transmission. There are two ears on the sides of this transmission that are not needed and were there for attachment points as it moved down the assembly line so I cut them off. At first I was going to raise the cab to gain the clearance needed for this transmission however now I am leaning towards the idea of notching the front cross member to clear the front pulley building new motor and transmission mounts and moving the engine and transmission down as a unit. Do to limited foot space and my huge feet the first idea that I abandon was cutting the floor boards and building a new transmission tunnel. One of the reasons I have decided to use this transmission is smoother transfer of torque. I thought this to be a good idea with all the added power and 54 year old running gear that has only ever known about 1/3 this amount of power I believe it may be the only chance it has of living for long.

Grant,
What are you using for a rear end?

I am using the stock two ton two speed rear

Good - I was planning on using my stock diff also.

And thanks for the input!