Hyster H40-XL-MIL Trans/Differential Issues

I picked up a "old" model A177 Hyster H40-XL-MIL forklift from a well known auction site and have been getting her back into running shape. Starts great, low hours, hydraulics worked after some lube, and overall a very nice unit. The issue that stumps me is it wont move forwards or backwards on its own. Fearing the worst I dug up the TM on the unit which is limited to the exploded diagrams and very basic info so no help there. Google searching lead to similar forums with people posting problems but no solutions. As a last resort I contacted Hyster directly and was pleasantly surprised to get a live human on the line and directed to someone with the entire manual set for the A177 unit. After a long discussion I was directed to test the transmission controller PSI to ensure it was indeed going into gear and it was all verified to be in acceptable ranges. The next step is a differential problem to which the guy said they "didn't have a diagnosis section for this issue."

Problem:
Front tires do not spin in the same direction and act like they are locked up if the unit is pushed/pulled. I had a shop lift the unit off the ground and we were able to spin the front tires in opposite directions (like a working differential should) but not the same direction. Even with no weight on the front axle it would not move the tires. The differential is mated directly to the transmission so there is no driveshaft to speak of. Had the transmission been the issue then the unit would roll free. The diff oil was low so it was topped off, I had hoped it was only "stuck" from sitting and could be broken free with a little push but no luck. I'm flabbergasted and don't want to send it to a shop just yet.

Inspected:
-Linkages
-Gear select (column)
-Fluid levels
-Monotrol System

TM-10-3930-657-24P

That explains why it would not roll off the trailer. Sounds like the pinion bearings are seized. The differential is the same set up as in any other vehicle, only is direct coupled to the transmission. Redneck fix: Drain everything, flip it on it's side, and pull the axle for repairs.

That or a valve has stuck and it is trying to put hydraulic pressure to the forward and reverse side at the same time.

NDT said:

That explains why it would not roll off the trailer. Sounds like the pinion bearings are seized. The differential is the same set up as in any other vehicle, only is direct coupled to the transmission. Redneck fix: Drain everything, flip it on it's side, and pull the axle for repairs.

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Makes sense, I hope that's it.

Jeepsinker said:

That or a valve has stuck and it is trying to put hydraulic pressure to the forward and reverse side at the same time.

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I don't think that's the case, even when the unit was lifted in the air and put into gear the differential acted with the same problem. I tested the PSI on all 7 points on the transmission controller making sure to monitor both forward and reverse at the same time for any differences. The snippets Hyster sent me said there should not be more than a 10psi difference between the forward and reverse. I've read that the monotrol system that allows the unit to creep forward while breaking may be stuck and allowing the fluid to just be dumped despite being in gear but that too was in excellent working order.

That sucks. Sounds like it may indeed be the pinion bearings. Is the park brake seized?

Jeepsinker said:

That sucks. Sounds like it may indeed be the pinion bearings. Is the park brake seized?

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Nope, it broke free with a little liquid wrench.

Does the engine slow down with the load from trying to turn the differential? If so, it would indicate the clutch pack is working correctly and the differential is locked up or the pinion is seized. If the engine doesn't slow down, it would indicate the drive gear on the pinion is turning freely, but that shouldn't prevent you from pushing the truck.

Either way, it looks like the transmission has to come out. On that model, the differential and transmission are one unit, with the differential attached to the outside of the transmission and then inserted into the axle housing. The pinion is driven by an output gear on it's shaft inside the transmission. The easiest way to get to it is pull both engine and trans, and then sepaerate on the floor.

Jeepsinker said:

That or a valve has stuck and it is trying to put hydraulic pressure to the forward and reverse side at the same time.

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in that case why would it not roll with the engine off? i assume it will not.

liftman said:

Does the engine slow down with the load from trying to turn the differential? If so, it would indicate the clutch pack is working correctly and the differential is locked up or the pinion is seized. If the engine doesn't slow down, it would indicate the drive gear on the pinion is turning freely, but that shouldn't prevent you from pushing the truck.

Either way, it looks like the transmission has to come out. On that model, the differential and transmission are one unit, with the differential attached to the outside of the transmission and then inserted into the axle housing. The pinion is driven by an output gear on it's shaft inside the transmission. The easiest way to get to it is pull both engine and trans, and then sepaerate on the floor.

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The engine does not slow down, but as m-35tom beat me to it..when why wont it roll?

m-35tom said:

in that case why would it not roll with the engine off? i assume it will not.

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It does not roll at all.

Pull the axles out and then see if it will roll. That will eliminate both the brakes and the wheels. Are the steer wheels locked up?

liftman said:

Pull the axles out and then see if it will roll. That will eliminate both the brakes and the wheels. Are the steer wheels locked up?

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he already knows the wheels turn, it is the carrier that does not turn. pull the drain plug and see what comes out. in almost any case the unit will have to come apart.

So how was your experience

lissa said:

So how was your experience

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It would be nice if people updated their threads with what they found the problem to be and what the solution to fix it was .

porkysplace said:

It would be nice if people updated their threads with what they found the problem to be and what the solution to fix it was .

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Problem was not identified or solved beyond what was stated in thread. Unit was sold to a wholesaler as parts were hard to find and the unit not worth the repair.

porkysplace said:

It would be nice if people updated their threads with what they found the problem to be and what the solution to fix it was .

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Yes I agree with you.

I would think parking brake I have seen some models with a driveline parking brake in side the trans