I purchased the Rendezvous used in 2007 from Jerry Seiner Buick in Salt Lake City as a 'Certified Used Car". Noticed the growl almost immediately and took it in to the dealership. They said that it was a 'characteristic' of the Versatrak all wheel drive. Would not fix. I should have demanded that they refund the purchase there and then and take the car back. There is a technical service bulletin regarding the issue that involves about $500-800 in parts and labor just to diagnose - with no definitive solution.

I did find that when using the spare tire, the AWD gets automatically disabled - and the problem goes away. I thought about finding the sensor for that and installing an AWD disable switch. Haven't done that yet - but it seems to be a probable solution to the crappy GM quality of the past decade.