Sand the diff rings with fine grit emery cloth, and build per AE's instructions. AE diffs always build up glass smooth. If they aren't smooth after that, replace the thrust bearing components. Use the black grease on the thrust bearing and the translucent lube on the diff balls. I have never had a problem getting glass smooth AE diffs.
Speed Merchant Rev7, Tekin, TQ Racing (wire), Team Tamale
RC Excitement - Buy where you race, support your local tracks.