I just had my stock diff rebuilt when new gears was installed about 1k miles ago. I've been to the track twice first time with no issues, the second time however, when i had the et streets on the car, it would spin both tires for a few seconds during the burnout then the driver side would stop spinning. I took the et streets off and but my 315 nitto dr's back on and made a pass, which it spun both tires during the burnout with no issues. What kinda problem am i having? I dont think the diff should be wore out after a couple passes.