in buggy i run diffs stock. fr 5000, cr 7000, rr 3000. i have used everything from 5000 alll the way through to 3-5-2 but fresh stock diffs are best for me. both truggy and buggy i run 40wt in front and 35wt in back. i know guys that run fr 20wt and rr 25wt. and seen guys race good with 50or60 weight and black springs all around. its all preference and what you are used to..id try stock 1st