The gearboxes on the Rocky platform suffer from a few common issues. When I got this car, the gearbox would consistently pop out of 5th gear. From the research I’ve done, it would seem this is a rather common issue where the nut holding the output shaft in starts loosening over time. As the other gears were fine and I didn’t have the time to do yet another gearbox swap, we drove it around for a while using just the first 4 gears. Eventually though the issue escalated, and now 3-2 downshifts were starting to get rather crunchy.
I wasn’t too keen on the idea of pulling out another gearbox, so I decided to try to solve the issue with the gearbox still installed. This would mean draining the fluids, splitting the gearbox and transfer case apart, and finally replacing the lock nut.
To get the transfer case out all driveshafts were disconnected, the underbody skid plates were removed, and all mounts holding the transfer case in were unbolted. After removing the bolts mating the gearbox and transfer case, they could be split open. This gave access to the output shaft nut. Worryingly though, it didn’t show any obvious signs of being loose. Having come this far, I decided I would install the new nut anyway and see what happens. Worst case scenario, the gearbox needs to be pulled and rebuilt or replaced anyway.