Large hole in diff housing MK3 Jetta TD 5spd, have replacement lined up but !!

[bigblockchev]

We found a quarter size hole in the bottom of the diff section of my son's 5spd. Cracks above that seem to come from inside. don't know whether he hit a rock or just cratered the diff.  It actually still drives fine !! We have located a  fairly cheap local replacement 5spd trans but the fellow says that it jumps out of reverse but works if you hold it in. We are wondering if this is likely a linkage adjustment issue or internal. Thoughts , experiences or ideas folks Cheers Dan

[Rabbit on Roids]

my tranny jumps out of reverse, but i think its a linkage issue, cause it didnt do it in my rabbit.

[burn_your_money]

Look up SMS or self machining syndrome if you want info on what happened to your first gear box.

[smutts]

Welcome to the "Why the F**k did VW use those stupid rivets?" club.
Fellow member right here.

Admittedly my towing an 88" Landrover the day before might not have helped.

I got 100miles @ 80mph before it siezed solid. Don't bother hammering a plug of wood into the hole to seal it. You will see why when the box comes off.

[commuter boy]

If it jumps out of 5th or reverse the synchros are gone and it will need to be rebuilt. 

I'm told it's caused by following VW's recommendation of never needing to check or change the tranny fluid.  Happens like clockwork on high mileage VW trannies.