Pops out of 3rd under acceleration.
 

This happens on a 71T that I'm looking at. The transmission was rebuilt at 88K and the car now has 100K. No grinding in any gears, smooth shifting, but under full acceleration 3rd will sometimes pop out. Any ideas?

if it is not the shift linkage it is the dog teeth, often in a rebuild the dog teeth on 3-5th are not replaced unless really bad, yours could have been on the bubble and the rebuilder did not replace them.

Jim

I will speculate that it is more likely the 3/4 operating sleeve that is worn out on the 3rd gear side. Jim

Both Jims have good points, but Mr. Sims' suggestion is most plausible. When that tranny was 'rebuilt' I suspect all the synchros were replaced along with any broken synchro hubs (dogteeth), but I bet that the sliders were overlooked. Sliders can usually last a little longer than the balk rings, but still wear down pretty good with regular use.

Hmmm, that sounds like internal work either way. Never heard of an operating sleve, would that require full dissasembly?

Ya, full teardown and since the 3-4 sleeve is on the input shaft, you'll probably have to get a pro to remove the 41mm nut (torqued at 166ft lbs) and press out the bearing...if this the same design as the later 915. Could it also be that the shift fork was not adjusted correctly and is not full engauging third gear?

I was wondering that as well, if there was an adjustment that could keep it from engaging fully... wishfull thinking probably.

Either way, dogteeth, operating sleeve or pinch fork, you'd have to do nearly a full teardown to get to it.

Your shift lever boot my be preventing the full engagement of 3rd gear or it might be a linkage adjustment issue.

Joe

That's what I was hoping to hear, but I doubt I'll be that lucky.

pull up the shifter boot and see if the shifter contacts the housing in 3rd. if it contacts the housing, a coupler adjustment might allow it to engage 3rd completely.