So on Dec. 29 I ordered a remanufactured ATK rearend from JEGS. My old rearend had newer gears but bearings started roaring. Took a while to get it, but the shop finally installed it on Jan. 21. I followed the break-in procedure with several short trips followed by cool-down and then took a road trip for 250 miles to complete minimum 200 mile break-in. I then followed the trailer towing break-in instructions with a few short towing trips. Then I resumed normal use, but avoided long trip towing as advised until after 500 miles. The shop recommended I come in to have the lube changed after break-in. They did that at 484 miles. At around 550 miles I notice a pronounced "chatter" or vibration when making left turns in the morning when the diff was cold. Then it starting doing that when making right turns. I went back to the shop and they added two more vials of limited slip lube. At first it seemed better, but has now resumed the vibration. Once it warms up, there is absolutely no vibration or noise of any kind. Anyone else experience this? I'm just trying to see if I need to initiate a dialog with JEGS about the problem. Just doesn't seem right.