2013 GMC 3500 dually Duramax diesel
The truck has been good except for the DEF system. In addition to a DEF tank system recall which required replacement, the truck has been in the shop three times in the last two years for DEF system repairs. Two of the repairs took the truck out of service for three weeks each. It's unclear how much of the time was mechanic's troubleshooting and how much was time waiting for expensive parts, but the time and expense was excessive. Unclear whether it's poor engineering design or poor quality parts production, but the time and expense required for these repairs are both totally unsatisfactory.