I have a slight rumble in my 12 Boss on track, left hand turns only and only while fairly heavily loaded. I have installed new front hubs, lower ball joints, tie rod ends and steering rack, they made absolutely no difference. The car had it's front lower control arm bushings replaced last fall. I tried 3 different sets of tires and wheels. I have looked at everything I can think of and can find nothing. It feels just like a front wheel bearing is going out although I cannot pinpoint if it is front or rear. I am now beginning to wonder about the Torsen differential, could it be going bad, I have the diff cover off, everything looks fine although it feels a little rough when you apply pressure to engage the Torsen, is this normal? The rear outer wheel bearings look good and feel fine. The diff oil looked nice and clean.

Maybe the right side bearing on the diff?

I will pull the caps and check it out. Thanks.

They look and feel great.

Axle bearings maybe

Took rear axles out, they look and feel great. They only have about 5000 miles on them. The differental bearings also look great. The diff feels a little rough while turning over with torsen engaged and no oil but smooths out with lubrication.