My Buggy has a 4600 in it and the diffs do pretty well. I'm pretty sure the 4600 is close to a 7.5. The truck is overpowered with a 5700 and the diffs are always in bad shape. Honestly though I think its something with that particular diff assembly. Might junk it and start fresh.
While were here and the truck thread is buried - I managed to intermingle all my springs. Have no idea which ones are the stock Gv2-t ones. Are they shiny silver or like a grey?