most g.m. transaxle had a couple differant final drive ratios offered. not that easy to change as it's the last thing to come out except on newer 4T60E. also some had differant tooth count on the drive & driven chain sprocket. not as far into the tranny but still need to know what you're doing. best bet is to visit local wecking yard of ck out hollander interchange & see what RPO codes will fit your rig.
bc
