Hi, I recently replaced brake shoes and wheel cylinders and when I put the drum on the drivers side I spun it and the driveshaft turned, so far so good. When I put the drum on the passenger side I spun it and the shaft turned inconsistently and then not at all. The three aftermarket manuals I have don't go into much depth on differentials. I did check fluid level and its ok. The truck only has 110k and I'm pretty sure this normal but I would like to make sure b4 I put it back together. I read all the posts so I'm not wasting any ones time but didn't see anything related. On the up side I learned that the thing on the top of the differential is a breather, good to know. thx in advance.