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'51 M transmission whine

M

Marty from MN

Member
I acquired a '51 M from my FIL that had been sitting for around 5 years.

Got it going again and now that it is moving, I found that the transmission is whinning. I figured I had better change the trans fluid. Drained out 4 to 5 gallons of water and not much oil. Filled it back up with new fluid.

That helped some but it still whines quite a bit. I also found that it pops out of 4th under a load (going up a long hill). I haven't tried 5th. All gears sound about the same, with the pitch going up for the higher gears. The whine goes away when not under load (downhill). There is no noise when in neutral with the clutch out. Also no noise when coasting.

Are the gears and bearings just rusty? Is a bearing going out? Should I keep running it to see if it clears up or will that cause more damage? Why is it popping out of 4th?
 

How bad is it whining? What type of sound is it, is it howling? Or is it gear noise? Mine has some gear noise but if I recall correctly all the farmall's I drove as a kid kind of whined/had some gear noise driving them around. Just like old cars.
 
It is louder than a normal gear whine. I have a Super M, a Super C, had a different old M for awhile. This whine is much louder than any of those rear ends.

There is also a very slight vibration when it is whinning. Just enough to feel it with your rear end on the seat.
 
It sounds to me like the pilot bearing on the mainshaft is worn enough and/or corrosion damaged and the cause of excessive noise. Popping out of 4th is what leads me in that direction.

You can remove the belt pulley or cover plate in 15 minutes and find out what you've got in there. Once off you can put your hand in and see if there's noticeable play between the mainshaft and the input shaft. Also you can determine what level of corrosion damage from the moisture. Sometimes the get a little surface rust on the gears and sometimes a lot and sometimes not at all.
 
Our Super H bearing was whining a tad...now whenever we change fluid we add a cpl qts of Lucas...much better
 
Cen Tex -

I won't be able to get that open until this weekend. Other than just looking for corrosion, anything to look for on the bearings? I never been into the rear end of an M, can you really see the bearing on the input shaft or counter shaft?

Would that shaft itself be loose? I would assume that if that shaft is loose at all the bearing is shot.

I'll check as much as I can from that opening.

Thanks for the advice.
 
You can't actually see the bearing because it is completely inside the input shaft, but you can definately tell if it has excessive wear. Get a good bright flashlight ready and you will find out a lot. You can get a heavy screwdriver or pry tool and apply force to the mainshaft where it comes out from the input shaft. Or if you're tough you can put your hand in there and try to wiggle it.

They'll normally work fine even with significant play because they're not too picky, but if it's popping out of gear then too much play could be the culprit.

The powertrain is fairly simple and will put up with a lot. The pilot bearing is changed by first removing the input shaft assembly through the clutch housing, which means first removing the clutch shaft. That's the hardest part of the deal.

Another thing to do is get both rear tires off the ground so you can turn them by hand with the transmission in neutral. Then you can pinpoint noisy bearings without the engine running.
 

That all makes sense. Thanks again.

I've been teaching myself how to work on tractor between shop manuals and this forum. I'm getting pretty good with engines, but haven't had to do much with the rear end yet. Just wish I had more time to work on them.

Also, are all of these bearing still available if they need to be replaced? Looking at the caseih site it looks like the parts are still active, but not sure if that means much.
 
Forgot to add a couple of things.

It's possible, but not likely that the whole mainshaft is "loose". The mainshaft rear bearing is held on one side by the pinion gear and by three steel retainers on the other. If that bearing is shot you can replace it with a "max" type that has more balls than the original one and thus higher capacity.

The pilot bearing will eat a $100 bill at the dealer. Check with Steel Wheel Ranch if you end up needing one as they advertise them now and are good people.

All the other bearing in the trans and rear are standard dimension ball bearing and can be obtained online or at a bearing house. Also, although I don't remember on the pilot bearing all of the other bearing are METRIC, believe it or not. Has to do with bearing standard that were in place long before M's came along!
 
All of the bearings are available. You can get any of the ball bearings from aftermarket sources although I believe the dealer has all of them. I haven't found the pilot bearing aftermarket, but Steel Wheel Ranch may have them.
 
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