Rebuilding Hydraulic Motor on my M936A1

[nf6x]

The hydraulic motor on my M936A1's hoist is leaking hydraulic fluid. As far as I can tell from the TMs, it's considered a disposable piece since I haven't found documentation of internal repairs or internal repair parts.

Have any of y'all had good luck opening up one of these gear pump style motors and replacing bad seals? Are they generally common parts, or custom parts for a specific motor? Unfortunately the dataplate on this motor is painted over, so I don't know who made it or what its manufacturer part number is.

I was working on the hoist gearbox today until my activities were tragically cut short by a thunderstorm. There's an unpleasant grinding/chattering sound when I operate the hoist, so I'm digging inside to look for problems. I hope it might be something simple like the brake band chattering on a rusty drum, but I didn't get into the brake housing before the rain started. The big leadscrew gear mechanism appears intact; no missing teeth rattling around in there. I cleaned out the crud from the inside of the housing, but then had to hastily slap the cover back on when the rain started. The shaft seal in the center of the cover is scratched in a couple spots and the lip loading spring has popped out, so I'll replace it. I'll seal the cover back on with RTV in place of the paper gasket that was leaking.

Is a grinding/chattering sound a common symptom of a failing hydraulic gear pump style motor?

The main hydraulic pump also "sings" when it's running, but it has a distinctly different sound than the rough sound of the hoist motor. I don't know if either or both sounds are things that I need to be concerned about.

Anyway, I did manage to free up the stuck sheave at the base of the boom yesterday, and I also removed the rusty set screw in the hoist drum and cleaned up the threads and the hole that the rope goes into. I expect to be able to replace the wire rope without major problems, but I'm putting that off until I finish servicing the innards of the hoist.

Oh yeah, another question: Do any of y'all have a preferred vendor of generic oil seals with online ordering? I checked my favorite industrial supplier (McMaster-Carr), but they don't carry that size of oil seal. I got the MS number from the parts TM and then looked up the dimensions online.

 

[m16ty]

I'm unfamiliar with the exact motor in question but most can be serviced/rebuilt. They are pretty straight forward taking apart, just make sure to keep track of where everything goes.

Odds are if you can get the info off the data plate you can find the rebuild parts at a hyd parts supplier.

 

[nf6x]

Getting the info off the dataplate will probably be difficult. It's thickly painted with at least one layer of CARC. If I remember, I'll take some pictures when I can and share them here, in case somebody reading the thread has an identical motor on their truck with a readable dataplate. I may dig in there to see what I can see anyway, but I'll feel more comfortable if I have reasonable confidence that I'll be able to locate the right internal parts before I open up the motor.

I wonder whether all of the M936 series wreckers have identical hoist motors, or if the motor is a generic part that can vary from truck to truck. If it's the latter case, then identifying my specific motor will be more important.

 

[M35A2-AZ]

My hoist motor is leaking into the winch gear boxes. Have not had time to work on it. Been working on the front axle, bearings in the right side all rusted up.

Anyway here is a my SS link to my thread.

HD Motor on Hoist leaking (M936)

I have noticed that the HD motor on the hoist winch must be leaking into the gear box on the winch and over flowing out of the gearbox vent and the holes in the side of the winch drum. Does anyone know if you can replace the seal or rebuild the pump? Also who may have a new pump or know were...

www.steelsoldiers.com

The data plate is on the motor on my hoist. If you can not read it I will send you a better pic.

Let us know how tow the repair goes.

 

[m16ty]

I've got a M936 wrecker bed at my shop. I'll take a look at the motor and see if I can read the data plate.

 

[nf6x]

My hoist motor is leaking into the winch gear boxes. Have not had time to work on it. Been working on the front axle, bearings in the right side all rusted up.

Anyway here is a my SS link to my thread.

HD Motor on Hoist leaking (M936)

I have noticed that the HD motor on the hoist winch must be leaking into the gear box on the winch and over flowing out of the gearbox vent and the holes in the side of the winch drum. Does anyone know if you can replace the seal or rebuild the pump? Also who may have a new pump or know were...

www.steelsoldiers.com

The data plate is on the motor on my hoist. If you can not read it I will send you a better pic.

Thanks! I think I can read the plate well enough, and your motor looks like it's the same as mine (see attached pictures).

Mine doesn't seem to be leaking into the gearbox, but it's leaking hydraulic fluid externally. My gearbox is also leaking gear oil, so I'm servicing its seals. Between those leaks and all of the greasy handprints I've been putting all over the truck over the last few weekends, I may need to buy a barrel of Purple Power to clean it all up!

While I have the sheet of paper in front of me, I might as well share the data I found on my damaged hoist shaft seal. It's the seal that's underneath the round plate in the middle of the big cover over the gearbox.

MS51000-131-2​

5330-01-254-6377​

2.125" shaft​

2.875" bore​

0.469" width​

Steel case​

NBR rubber seal, loaded lip​

I've ordered one with the same dimensions from Reid Supply, and hope to get it by next weekend. I haven't ordered form them before; I just googled for oil seals and found them. Their web page says that particular size is discontinued, so if you also need one of these seals then you might need to find another supplier.

 

[73m819]

The hoist motor is the same as the 543 and the 816, same bed, same crane, same rear winch only 936 is hyd. drive, where the 543 and the 816 is chain drive.

 

[nf6x]

Dang it, now I need to go outside with a flashlight to climb on my M543A2 and take a close look at its hoist motor.

 

[nf6x]

AHA! The hoist motor on my M543A2 is not the same as the one on my M936A1. I wouldn't be surprised if they can be swapped as complete units without any problems, but their internal parts may not be the same. The external castings are clearly different.

The beds are very similar, but not identical. For example, the welding bottle mounts are located and built differently, probably because the muffler on the M939 series chassis forced one of the bottles to be moved to the other side of the truck.

I think it's fun to see what has changed and what is exactly the same on two trucks that are 20 years and two generations apart from each other.

 

[gimpyrobb]

I think it's fun to see what has changed and what is exactly the same on two trucks that are 20 years and two generations apart from each other.

Time to get the camera out and post some pics. I think that would be very interesting.

 

[nf6x]

Well, it's been a rough morning! One of my doggies had a seizure, so I rushed her in to the vet. She's doing ok now, but they're keeping her today for observation. So here I am posting to keep my mind occupied! If all goes well, she should be coming home this evening, and hopefully the blood work will provide a treatable explanation for her seizure. I'm staying home from work today, so I'll probably hang out here a lot. I'm just glad that it happened before I left for work so I was here to help her.

I took some pictures earlier this morning. First, here is the hoist motor on the M936A1. Based on the dataplate shown in M35A2-AZ's thread, I believe that it was made by Parker.

​

Now, here's the motor on my M543A2, which should be leaving for its new home in a week or three.

​

Its dataplate is still readable, and it's made by Garwood.

​

 

[73m819]

I would guess that the parker is just the replacement for the garwood, should bolt up, is the motor for the rear and front winches parker also ???

 

[nf6x]

I would guess that the parker is just the replacement for the garwood, should bolt up, is the motor for the rear and front winches parker also ???

Good question. I haven't been inside the box at the right rear corner of the bed yet; that's where the rear winch motor is located, isn't it?

 

[73m819]

should be

 

[Ord22]

try this, google Garwood and see what comes up. You never know.

 

[Csm Davis]

Good question. I haven't been inside the box at the right rear corner of the bed yet; that's where the rear winch motor is located, isn't it?

Nope only thing under the box is hoses and valves the motor for the rear winch is where the pto shaft used to go, hooked to the chain drive. All of the winches are the same as the older ones just driven by a hydro motor instead of a pto shaft.