What size is the gear. If you dont have a pinion depth gauge then put the pinion in use a set of dial calipars and you are going to like this one but if you have some bushing or seal installer you can put them in place of carrier bearings, slide a peace of tubing threw the holes and mark the tube at the half way, and measure from bottom of the pinion and the middle of tube and that should get you close to your pinion depth and what shims to start with. I have not seen to many rears that did not have no pinion shims. Well good luck and let me know if this helps.