I just got my LJ back from the shop where they installed 4.88s for me. After I picked it up, I noticed a drive shaft vibration at certain speeds. Anything over 50 mph and then I let off the gas and decelerate there is a bad vibration. Once I drop lower than 50 mph everything goes away. Then anything over 70 mph regardless of whether you are on the gas or the brake, there is also a vibration. Under 50 mph you wouldn't even know anything is wrong. Here's a little background info. Rear tires are 2000 miles old and are properly balanced, I have a 2 month old SYE and rear CV driveshaft. While it was there getting regeared, the axle shafts were also freshened up with no bearings and seals. Any ideas of what could be the culprit of this vibration?