2001 996 Turbo with TipTronic. 88k miles - many on track, over 600 hp since new. Engine and transmission have been rebuilt.
The car has gradually started making a rumbling noise, similar to driving with spike tires on dry road. I thought it was just the Pirelli rears making noise but it has gotten gradually worse. Turning the tires over made no difference. I have not been able to lift all four wheels to try to diagnose but now think it is either the differential or a rear wheel bearing. Do you knowledgeable and experienced guys have suggestions of what may be the issue based on the above description?

 

CV joints on the axles maybe?

 

I should have included: Entire rear axles were replaced a couples of thousand miles ago.

 

Based on described symptoms, it certainly could be a wheel bearing. Get her on a lift and look for play.

 

Thanks for the feedback.
I am away from home. Does anyone of you recommend a mechanic around Glenwood Springs, CO?

 

if you suspect a worn wheel bearing, a simple yet effective way to further diagnose this is to "slalom" left/right a few times. if the noise abates on turning then the wheel bearing on the opposite side of the turn indicates it is the source of the rumbling. e.g.. turn left - noise stops - check right rear, etc.