FYI for Cadillac CTS AWD issue (dealer fix informative)

This was NOT my car but a friends. The fix was insightful and I thought the GM techs and enthusiasts might find this interesting and possibly useful down the road.

Final update: Problem solved!!!

The issue of driveline vibration & thumping noise on my CTS4 during times of mid-to-high load/rpm/acceleration (i.e. high driveline torque) was resolved yesterday at the dealer.

In consultation with GM Tech, the dealership's service folks succeeded in eliminating the torque-induced vibration/noise problem by shimming the AWD transfer case crossmember down slightly, using a 1/8" alignment shim on each side of the transfer case crossmember.

It appears the stack-up of powertrain tolerances (together with vehicle chassis manufacturing tolerances) on my AWD CTS allowed the transfer case (and/or the transmission case) to momentarily 'ground out' on the driveline tunnel anytime the powertrain was loaded up... (but only when all of the powertrain components had reached normal operating temperature).

Kudos to my dealer and the GM product support network in getting this issue resolved on my car. They did a great job. :thumbsup:

On the way home from work today I managed (as usual) to bury the accelerator once or twice (maybe a few more times than that.. :sneaky: ).. and instead of hearing some episodes of driveline vibration & noise, all I heard was the sweet sound of the engine doing its thing. Hey, you gotta love it.

What a great car this new CTS is.