I have 99' 2dr 4wd blazer that I had to recently swap out a bad transfer case. While I was at it I replaced the U-joints and put all new fluids in and greased everything. Anyways after getting everything done and test driving I noticed a slight vibration on deceleration at all speeds. It only happens for a second or 2 and its barely noticeable. I marked the drive shafts to keep them on balance with the differentials. The transfer case was used (47k miles) and was correct number. So any suggestions on what it could be?