depends how far off,I know the pinion for motive gear comes stamped with a pinion depth to check with a pinion depth tool, they are expensive and not worth it unless you want to do a lot of them and sometimes might still need adjustment after fact. I know the pinion head comes with a +-.002 thousands of variance from distance marked on the head. What was your factory pinion shim depth, I always start there and its usually pretty close most of the time, For me its usually always too shallow by a few thousands, but its a good starting point.