One problem related to transmission solenoid has been reported for the 2006 GMC C4500. The most recently reported issues are listed below.
: the contact stated while traveling no particular, the transmission downshifted into first gear. The vehicle was pulled over and the dealership sent a technician to the vehicle to deprogrammed the codes to drive the vehicle to the dealership. An internal wire harness, pins connectors, and solenoid were replaced, but the problem persisted.