I went to the track 2 weeks ago. I have my 2-step setup to launch at 5k building around 6 psi. This worked pretty well on the street when I tested it (no hop, decent spin). I went to the track with 20 psi of tire pressure. I did exactly as I did on the street and it hopped like you wouldn't believe. I have a TII Diff with 4.33 gears, nylon bushings, and PPF Reinforcement (welded steel).

Since that run, I have been getting a lot of whirring/whining from the back of the car on decelleration. My mech. checked the diff. and everything checked out ok. I had been running the TII Diff with all of the above mentioned supporting mods for over a month before I went to the track and had no whirring. Now, it's starting to get on my nerves.

Any ideas what it could be? Wheel bearing?

 

the only thing that comes to mind is a problem with the diff. i cant see anything else causing those classic signs of a "failing differential"

 

Let's assume for right now that the differential is fine. Any other ideas?

 

my stock diff did that after a bad wheel hop session at the track. it was whining like that for a year then exploted when i sifting to second on a hard street run

 

Whining and whirring I would expect to be gears in the rearend.

As for axle hop at the track and not on the street the track probably had much better traction...