Okay. So. 2012, GMC 3500 desiel dually. I had a 2007 Chevy, same model, that had no exhaust brake and it stopped my damn trailer better. I bought this "new" 2012 truck for the exhaust brake and the "better" towing capacity. It has no suck back and stop. It is weak as well. Everything on it is...
The allison in my fathers 03 duramax is not shifting and as a result it tops out at 20, 40 or 60 mph when it wants to. The truck is completly stock any help would be appreciated.