First thing I do when I get a new buggy is strip it down to the chassis and put it back together with locktite on all metal to metal screws. While I have it disassembled I do all of the diff and shock fluids. This is the best way to get to know your buggy top to bottom. For hard dirt I would personally go 5F-7C-3R. This set up will help pull out of corners rather than sliding through them.