Fun with a B21 Differential

[ovrszd]

Sandman,

From the looks of things, this isn't the first time this area of the tractor has been apart. I think some of the reason the gears have worn is it was improperly shimmed at some point in the past. (there was 1 shim on the ring side of the differential and 5 shims on the other side).

I am considering taking the assembly (trans/diff) to a shop that specializes in differentials and hoping they take pity on me and can help align everything.

The last thing I want to do is to take this thing apart again, what a pain! I would consider taking it to some of the kubota dealers around Sacramento if they weren't charging extortion rates for parts (30% above kubota list) and labor ($85/hr).

-Lucas

Yep, I think you are headed in the right direction. If you had found virgin territory here and were sure it had not been previously taken apart, I would have said keep very close track of the shims as you disassemble and put it back together with the same setup and you'll be fine. But since you have discovered tampering, you have no choice but do a complete setup.

The shims are in place to offset differences in the case, not the gears. The gears are manufactured under close enough tolerances that the same shim setup will work with a different set of gears.

In your situation though, you have no proof that it was properly set up the last time it was assembled. You actually have evidence that it might not have been since it failed again.

You are a brave man to tackle this and thanks for posting the progress. I'm anxious to hear the outcome.

 

[scott_vt]

Mornin Yubby,
Boy are you in deep I like your thinkin on bringing the geared unit to someone that can set it up properly ! Even to install the new gears with high spot bluing and dry run it to check the wear pattern on the mating teeth is a lot work ! Good luck with whatever direction you decide to go and post your results.

 

[bx23barry]

If you are around sacramento take it to river city differentals in rancho cordova and see if sean can help you out. He is way kool.

 

[AndyMA]

One more emphasis on making sure it is shimmed properly. A front differential on my Ford 2120 had the ring and pinion replaced and was not shimmed perfectly. It lasted exactly one week and they had to be replaced again. Blew the teeth right off both gears. I still have the parts to remind me of the $1600 repair.

andy

 

[RobertN]

If you are around sacramento

Brian at Sierra Tractor in shingle Springs is pretty good too...

 

[yubby]

Well the saga continues

Finally got everything apart and cleaned up. Reconstructed the new differential, and discovered what torque can do to shims and 1/8" thick snap rings.

See attached.

--Lucas

 

[yubby]

Another thing I noticed is that the bearings on the pinion spun in the housing when everything was bolted back together. In automobiles this is usually very bad and indicates that the bearing locked and spun up at some point (or had tremendous stress). Is this normal/acceptable on a small tractor?

I don't want to unnecessarily replace the differential case, but am definetely leaning that way unless this is normal? (see attached pictures)

Thanks for all your help and comments!

Lucas

 

[dullpain]

If you want to tighten the fit of that outer race in the bore of the case , you can take a center punch and punch all the way around the bore, do a couple of rows. This will raise some of the parent metal and make an interference fit if bore is not too large. I believe that Loctite also makes a liquid chemical product for this purpose , can't remember the name tho. Loctite is the brand name of thread locking compound , should be able to find it at a good NAPA parts store.

 

[bx23barry]

I’m pretty sure those bearing shouldn't spin in the case. Try the centerpunch/green loctite (stud and bearing) thing.

 

[sandman2234]

When you knurl the case to allow the bearing race to fit better, make sure you do it equally all the way around. Keeping the bearing centered will probably make a difference.
Another way would be to use some very thin shim stock to take up the space.
David from jax