We have completed several Pinion nut repairs and along with that we have encountered a few that the threads have been pull or stripped. There have been plugs held in place with RTV, Epoxy, Permatex No 2 gasket maker.
We have tried a few things to make repairs, the best we have found is to use a 7/16 x 20 taper tap to cut threads, it will start with out any drilling the hole any larger. Use a 7/16x20 x 3/4 inch cap screw and a copper washer, a bit of 242 Blue Loctite.
There is just enough room for the hex head to clear and thread in, an open end wrench will need to be used to tighten the bolt, there isn't room for a socket.
Les