[Blue Bowtie]

I'd suggest you return it to the dealership and report the problem. Even if they find nothing, you have a record of a reported problem. That may extend your warranty coverage if something occurs after the normal warranty expires. If you reported it within warranty, they should be required to repair it under warranty.

All these reports of problems are also what drives the TSB system, and causes further examination of common problems by GM. If something is discovered to be a common problem, but not sufficient to mandate a recall, a Technical Service Bulletin is issued, and your complaint should result in a free repair so long as you reported it within the warranty period.

There have been some problems with shudder caused by the transfer cases and the aluminum matrix core within driveshafts shifting, and nothing is externally apparent. You may want to advise your friend to do the same. Most dealerships really WANT to help, since they get paid by corporate for any warranty work.