Rebuilding a M37 transmission

[Roger Friedrich]

I was wanting to get some information about rebuilding my 4 speed Transmission. The problem I have is when I'm going slow in a parade the transmission will come out of gear. I just clutch it and can put it back in. I've pulled the transmission and motor for an overhaul and thought I would repair the transmission.

How much experience does one need to tear down the transmission?

I was thinking it probably the synchronizer but could it be any thing else?

I did review the TM on the website but I know how that goes when you read something then start it thing are different

Thanks for all your help

 

[foxtrk2]

I wouldn't thin its needing a total rebuild some timed the bushings on the shifting shafts need replaceing or th eindent ball bearing an dspring are the problem not usually much further than that on the ones ive done hope that's helps a little

 

[The HUlk]

How much experience does one need to tear down the transmission?

With a good service manual for the transmission I would think anybody with general mechanical skills and access to any necessary equipment should be able to service it. I have not seen the TMs or worked on this transmission so I couldn't say if the TMs are what I would consider good service manuals or not.

 

[Warthog]

I rebuilt a SM465 this spring. First one I have every done. It wasn't too had.

Take many pictures as you disassemble and a engine stand is very helpful.

 

[M543A2]

I suggest finding a Motors Truck Repair Manual of the age era of the truck. It will have detailed instructions. You can probably find one at a library or online like Ebay.

 

[GUNNY 155]

If you have it out I would do a tear down and inspect on it. Replace all seals and gaskets. Bearings as needed. Now specific to your problem. Popping out of gear can be a worn syncro ring issue and if they are worn I would replace them. Most often the problem is found in the shift mechanism. Worn or broken springs is one culprit. If you need springs PM me I have a bunch. The other place to look is the shift lever pin which is located up by the top boot where the shifter stub comes out. The hole where the pin goes in the cover casting gets worn and you get a lot of side to side play this will not cause the popping out of gear but can make shifting sort of a fishing expedition. Mid West Military has complete NOS covers which is the way I went. I also have a used serviceable cover if that would help you. If you have a TM and some mechanical skills overhaul should not be a problem, the TM goes through it step by step.

 

[Roger Friedrich]

Thanks for the information and encouragement about working on the transmission. Currently the engine is getting all my free time and then I'll get working on the transmission when I get the engine back in the truck. Hopefully I'll have it all going by spring if the money doesn't run out hahaha.

 

[T. Highway]

You will first want to determine which transmission you have. Early or late model.

There are significant differences in the late model transmission, that cured problems that naturally occurred in the early model. The one you mentioned about it slipping out of gear was common in the early transmission. A snap ring land / shoulder failure on the gear cluster shaft would let the cluster wander when the load was added and removed.

Bert