One problem related to automatic transmission has been reported for the 2006 GMC Sierra 2500. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2006 GMC Sierra 2500 based on all problems reported for the 2006 Sierra 2500.
2006 GMC diesel with allison transmission. . . Lines to transmission cooler leaking. It is a fire hazard. . . From what I read on the internet it has been a problem with all the transmission lines installed on this truck.