The shift fork inside the 915 transmission has a very common issue of the tiny M6 nuts/studs loosening. This has a direct and large impact on shifting, as it provides a pivot point for the shift linkage moving forward and back inside the gearbox. At worst, there is not enough travel to even get into gear.
There is no way to tell this is happening without draining the gearbox fluid and dropping the fork plate on the bottom of the transmission. About 90% of the plates we drop show some amount of fretting, and many have damage to the fork from contacting the rotating gears.
Our billet aluminum plate replaces the original cast part (the magnesium versions have especially weak threads). We tap threads all the way through and install long bolts from the inside backing them up with locknuts on the outside of the plate. This adds considerable strength and locks everything in place with the nuts.
The kit comes with an anodized upgraded plate, high-grade through bolts, washers, locknuts, new mounting washers and locknuts, gasket, pre-applied thread sealant so the new bolts won't leak, and instructions.
Installation is simple, but does require completely draining the gear oil.