Wanted: M56 Rear Facing PTO Driveline Parts, shafts, etc.

[U404S]

Hello, I'm starting a new project and am looking for all of the driveline parts from the backward facing PTO shaft that would have operated the welder mounted in the bed of a Dodge M56 Tool truck.

I have an M56 with a lengthened M37 troop bed in place of the boxy tool/welder bed. I want to replace the M37 bed with a flatbed and mount a 25,000 pound capacity hydraulic Braden winch behind the cab. My PTO has front and backward facing shafts. The front operates the stock Braden winch in front. I want the back PTO shaft to operate the hydraulic pump that powers the big winch.

The big hydraulic Braden winch came off of the bed of a Mercedes Benz Unimog Model 406 that was rigged for railroad work. I thought beginning with the original M56 slip yoke, shafts, pillow block, etc. would be a good place to start before trying to cobble together everything with new parts. I'm open to better ideas if anyone has any.

To make it easy, I might be able to travel and remove this stuff from your truck or pick it up. I'm in Jacksonville, Florida but will be in the states between here and Upper Michigan in the next month or so, the Carolinas in February and Texas in March. Might even buy your unwanted M56 truck if that is easier. It's all part of the hobby. Thanks, Jerry

[Cal_Gary]

That's quite a project, Jerry!
I don't have any of the parts you seek but was wondering if the PTO will have enough RPMs to turn the hydraulic pump to move the fluid required to drive that winch? I have no expertise with hydraulic pumps but would think that the PTO shaft can only turn as fast as the gear ratio allows (coupled to the turning transmission and engine, of course).
Just an odd thought.
Gary

[just me]

There are pumps that work at low RPM. As always, there is engineering involved. But the project is definitely do-able.

[U404S]

This is a good point Cal_Gary and not an odd thought at all. From time-to-time, I have vaguely wondered about this piece and to no real conclusion.

The Type 406 Unimog this came off of had a two-speed PTO and it wasn't clear which speed was used to power the winch. So that is one problem.

The second is the Unimog probably develops its maximum torque and HP at different RPM's than the 230. However, since I never determined which engine or output that Unimog was outfit with, or been able to find the statistics of the winch itself, the opportunity for accurate engineering is heavily prejudiced. Just too many unknown values to enter into the equation I don't really understand.

So, I'm going to see how it works with the pump it came with. My engineering test will be that if I can drag the truck backwards with the wheels locked with the engine spinning at 1,300 - 1,600 RPM's, then it will be good enough. If it can't pass that test, I'll copy the specifications for the M37 PTO output (probably in my manuals somewhere) and take those, and the current hydraulic pump, to one of the Jacksonville driveline shops and see what they recommend. Not an optimal method overall, but I'd rather have the winch under-powered than over-powered. I hope Just Me is right that it is possible to make this work contigent on the pump.

The other piece I don't understand is how hydraulics in this application work. For example, if the inputs to the pump are too weak, will the winch spin at its specified speed, but give up under load, or will it pull to specified capacity, but just do it slower? I suppose anyone who ever operated a dump truck carrying different weight loads could answer that one easily, but I don't have that experience.

Maybe I'll upload some pictures of the winch tonight in case you guys have an interest in seeing it. It's a monster compared to the Braden in front. I have a couple Mercedes Type C winches that weigh 380 pounds each. I thought those were big. This one might be close to twice that. Hard to say exactly.

Thank you both for your input.

[rickf]

You can probably find any info you need here. http://www.hydraulicsuperstore.com/merc ... gJIj_D_BwE

Or here.
https://crossmfg.com/parts/product-id/gear-pumps-motors

I went through all of this when trying to find the right pump for an old loader.

[U404S]

Thank you RickF. These are great resources and probably all I need to address the pump side. I dialed Bill L. near Ocala thinking he may have some PTO parts, but he has none. I also heard there is an M56 Contact Maintenance truck in Sanford, FL so I'm going to try and find that one. Current condition is unknown, but there is supposed to be one there.

In case anyone is interested, I am uploading a few pictures of the big Braden when it was mounted on the Unimog and also of one the Mercedes Benz Type C winches. This Type C is completely reworked and powder coated. My other one looks pretty rough, but works.

[U404S]

Some more winch pictures:

[U404S]

Mercedes Benz Type C PTO Winch. The circle to the right of the drum is a handbrake.

[Cal_Gary]

This M56 just hit eBay:
https://www.ebay.com/itm/Dodge-military ... :rk:6:pf:0
Gary

[U404S]

That's a nice one; pretty complete, but, regrettably, the starting bid is well beyond it's value to me. It would be interesting to see what the next owner does with it.

[Kaegi]

I am pretty sure the M56 unit is not driven by the winch PTO on the tranny. i think they used the Davey PTO system that is run off the back of the transfer case. The davey unit is spliced inbetween the tcase and the rear driveline. The Military ordered Dodge Power Wagons also came that way. some even have the power wagon emblems removed off the hood and replaced with Davey PTO emblems. it is a massive thing that runs belts up to the welder gen in the bed. it can be disengaged from the rear driveline

[U404S]

Thank you for that Kaegi, I didn't think of that. Finding one of those kits might be tougher yet.

I just assumed that because this truck had the front and rear PTO output shafts that the back facing shaft was used for the welder (front to winch).

Regardless, I am thinking now that I can get a machine shop to make me a 2.5 foot shaft that connects the back facing PTO shaft and coonects directly to the hydraulic pump output shaft. The PTO is 1.125" with a .25" keyway and has a retaining pin/bolt boring through it. The hydralic pump dimensions can't be much different. I won't use universal joints, gears or chains, just direct drive bolting the hydralic pump to a neoprene base to reduce shock. This ought to work and be a lot cheaper.....right?

Uploaded an image of the backward PTO shaft. I have read these are rare and I have noticed only the single direction PTO is mentioned in my manuals.

[rickf]

You will want to use Lovejoy connectors to connect the pump to the shaft since you can never get perfect alignment from shaft to pump. They will absorb slight differences. You can also go from one size shaft to another if need be using them.

[U404S]

Thank you RickF.

[Kaegi]

the dual output PTOs is what came on Power wagons. nice unit. I would run ujoints because the dodge frames flex alot (on purpose) and the parts are standardized and available at any driveline shop. in fact if you figure out the shaft sizes and length you need you might find a universal driveline kit off the shelf that you cut to length,. I have done it that way before.