The most commonly reported problem with the GMC Envoy SUV's transmission is a complete transmission failure, according to car repair statistics website CarComplaints.com. Some owners also report rough shifting or problems shifting into certain gears.
Transmission problems have been reported for almost all model years of the GMC Envoy, though serious issues are most frequently reported on models produced from 2004 to 2006. Transmission failures have been reported on vehicles with as few as 20,000 miles and usually necessitate a full transmission rebuild or replacement. In some cases, the vehicle becomes stuck in a single gear when the transmission fails, while other owners report a complete loss of power in any gear. The latter behavior may be due to the failure of the Envoy's torque converter.
Many owners who complain of rough shifting behavior first experience this issue after a sudden downshift occurs when driving at highway speeds of 60 to 75 mph. The Envoy's transmission sometimes suddenly shifts to a lower gear at these speeds for no reason discernible to the driver. After this downshift occurs, owners frequently report that the vehicle begins shifting roughly between some or all gears. No cause for this problem has been definitively isolated.