MTFCA Forum

I thought the rear differential had come apart. Started disassembly to diagnose and found the pinion key had sheared. My question to those with more experience is this: can I clean up and reuse the drive shaft and replace the pinion key only or do I need a new drive shaft. Photos attached.

Both the taper and the keyway look bad to me. I wouldn't risk it. That's a critical fit, and a failure at that point will disable the car and could leave you brake-less.

can I clean up and reuse the drive shaft

Pat is right...absolutely not

Any real safety factor in a T is all but non-existent and adding potential failure modes is not something I would consider doing.

Thanks both. Yeah, that's what I was thinking too. When it first failed I had no brakes... vs. normal with bad brakes.

Another consideration would be alignment of the new pinion if you tried to re-use that shaft. If it didn't come loose almost immediately, it would probably have enough run-out to destroy itself in short order. I'd think it would be difficult to impossible to set up the gear clearance correctly with a new pinion on that damaged shaft.

Model Ts boil to maximize fuel economy and minimal braking helps improve tire mileage. Ford generously includes these features at no extra cost.

In this case, the taper is too far gone for my taste.
I have saved cherry original shafts that had a sloppy key way by recutting the slot 180 degrees out.
They gotta be near perfect for the effort. This one goes to the cut for warford or iron pile.

That driveshaft has had it, I would suspect the pinion gear is also. The fit of the taper is as or more important than the key to keep it from spinning and shearing the key again. The gear should lock down on the shaft even without a key in place and not rock....

speedytinc wrote: ↑

Sun Oct 24, 2021 11:10 am

I have saved cherry original shafts that had a sloppy key way by recutting the slot 180 degrees out.

With all due respect, in my estimation, that is not a good idea.

Only seen the key sheer if the pinion and gear at tapes
Are not good
My suggestion fund another drive shaft or pinion and check the fit with out a key

Ruxstel24 wrote: ↑

Sun Oct 24, 2021 11:49 am

That driveshaft has had it, I would suspect the pinion gear is also. The fit of the taper is as or more important than the key to keep it from spinning and shearing the key again. The gear should lock down on the shaft even without a key in place and not rock....

This is true. One thing I do is lap every gear/shaft so they hold on their own as a taper should.
Some need more than others to fit together properly. Same with axle shafts & hubs.