Two problems related to transmission not engage have been reported for the 2004 GMC Envoy. The most recently reported issues are listed below.
Car will not engage in park position. Car will roll forward or backwards causing safety concerns of injury or another person or car.
Shifter cable bushing became disengaged from the transmission. Shifter lever floated freely through gears. When engine stopped, it would not go into park but remained in neutral and began freely rolling backwards in my driveway. Emergency brake had to be used to stop the car. I understand this is a fairly common problem with this make of vehicle. This part should be recalled.