Update and new questions- I pulled out the differential, and removed the old torque tube bushings and seal with a 6 ft pipe.
1. both bushings and seal were trash, with small pieces of brass in the tube and banjo.
2. The rear bushing was worn into an egg- oval shape.
3. The propeller shaft is worn down about 1/16th at that rear bushing location.
4. the pinion-to-propeller shaft coupling rivet was broken in half and loose
5. The pinion was wiggly loose on its splines and came right off when the rivet fell out (no puller needed)
6. the gear teeth and bearings look ok, but have play and lash.
Could replacing the broken pinion coupling rivet and torque tube bushing solve the problem?
Or are the broken coupling rivet and bushing wear the effects of some accident or misalignment that has trashed everything else?
What needs measuring to see if the 3.90 setup is worth fixing? (yes, I can cannibalize just the 3:90 ring and pinion, or the whole assembly for my old diff, but they might be bad or mismatch?)
And does anybody know specs for the coupling rivet to source locally? Are there oversized ones/
