hevmando
Well-known member
I just bought a 2006 GMC 2500HD 6.6 Duramax with 6 spd Allison. Very happy with the truck but have noticed a ringing noise when it shifts from 1st to 2nd, and 2nd to 3rd. Last for about 1/2 second and sounds like a bicycle bell. Anyone have experience with this? Also it is getting 11-12 mpg on 90-10 wintermix. I have read about a new chip, an egr block, pcv reroute, and new exhaust. If anything, I baby this truck and was wondering if there is an easy/relatively inexpensive change to improve mpg.