Ah, the joys of overpowered 914's.
I have enjoyed 2 tranny failures.
Coming out of turn 3 at SP, felt a little bump and the engine rpms went up crazily. Hmmn, car jumped out of gear. Put my foot on the clutch but the clutch was on the floor.
The pinon lost 2 teeth and one became caught in the ring gear that locked the rear wheels (the little bump). This locked up the tranny and took out the main shaft, clutch, and flywheel beside the complete tranny rebuild.
Repair approached 3K. Maybe time to convert to 915!
At the time the only one making a tailpiece to convert a 915 to fit in car was Vellios. Tailshaft conversion was 1800-2000 plus the cost of obtaining a 915, rebuilding that tranny, new clutch, pressure plate, disc, etc. approached 9K. Decided I could repair/replace 901's every couple years for that kind of money.
Go to 914.com and do a search on this problem.
You may be hard pressed to convert to 915 and still make VIR.