The first gear syncro is getting really bad in my street car 914, but no problem, I have a spare tranny I picked up a few years ago so thought I'd just swap them out. But the spare tranny didn't have a speedometer driveshaft in it. Tried to swap the driveshaft from my current tranny, but it didn't fit. It appears the diameter of the gear on the end of the shaft is too big. It locks up and won't spin as you push in the shaft and it's surrounding bushing with the 90 deg. cable drive. The two tranny's involved are different versions of the end case. Both are side shift. The original has no bottom access plate on the end cover. The spare does have an access plate. I wasn't aware that there were any differences in the internals. Am I missing something here? Any suggestions?

Andrew B.

Nope the same speedo drive but you seem to be describing both a tail & side shift rear covers
There is a securing pin/bolt?
Many of the covers have seen some (significant) wear from a loose speedo drive gear & angle drive.

Have the retaining bolt out.

I'd previously not been driving the speedo drive bushing all the way in as I was feeling it lock up before getting it all the way home. Just tried driving it all the way in, in the hope that it would free up once it got in all the way. No luck. Still frozen up.

Very puzzling.

Andrew

Ok, mystery partially solved. The brass speedo drive gear sticking out the end of the expansion bolt is the wrong diameter! It has a 21.8 mm o.d., when it should be 22 mm. Too big means it binds up the whole gear system as the drive gear tries to go into it's bushing in the end cover as you tighten the end cover down.

Next question is where did this odd sized drive gear come from? 911 part? The tranny case's serial number identifies it as a mid-'71 case. I got it from a PCA friend that was moving out of the area. I'll see if I can track him down to get some more history on this tranny which might give some clues. In the mean time, I'll find another drive gear for this box.

Andrew