I’ve started to disassemble the transmission and engine of our newer Jetta.
I’ve found fifth gear worn (was run with low transmission fluid), and the bearing on the tip of the output shaft was worn as well. I’ve drilled the rivets that hold the ring gear to the differential and I will replace them with ARP bolts. I also bought an overhaul kit which came with bearings seals, and gaskets.
The engine had 125 PSI of compression in cylinder number 4. I’ve found the cylinder had worn 0.017″ which wore the piston lands and allowed the upper compression ring to cock in the lands and break the piston. The head also has cracks between the valves, a new one is $1500+ from VW, I think I’m going to reuse this one.
For those who are interested in specs. : 90 Jetta, 1.6 IDI Turbo Diesel code MF, 020 5 Speed Transaxle Code 4S. 
