View Single Post
      06-14-2011, 07:17 AM   #6
I'm suckin gas but I'm haulin ass
Rapture's Avatar

Drives: 2016 M3 ZCP MW/SO
Join Date: Sep 2010
Location: OC, CA

iTrader: (18)

I have the same sound... I have concluded it is the belt slipping on the pullies due to the DCT trans shifting faster than the engine can down rev for the next gear.
The noise was barely audible with stock pullies/belts but has been a bit louder after MS underdrive pullies/belts.
The small amount of slipping is ok, but if it slips more than what we normally hear then it may cause premature belt failure, I suppose. My Cobra would slip the blower belt a little on every shift due to the same problem... If it started to slip badly on acceleration and I didn't notice it would just blow the damn belt up.
I didn't build it hoping for your approval, I built it because it meets mine