One problem related to transmission stuck in gear has been reported for the 2004 GMC Envoy. The most recently reported issues are listed below.
When I first bought the vehicle the transmission was shifting eratiecly for a while. I took vehicle to dealer, and they said nothing was wrong drive it until it breaks. 3 months and about 3,000 miles later I had not had another problem. Until I pulled up to a stop sign at a busy intersection. I checked for trafic and went to pull out except that the Envoy would barely move. It was like the brakes were on or something was holding the vehicle back from moving. The cross traffic was quickly approaching and I had no choice but to slam on my brakes and hope the other person didnt hit me as I was sticking out in the intersection. The other person swerved and missed me. I pushed down on the accelerator again and slowly rolled through the intersection. I stopped on the other side of the intersection and tried to start again. The same result of no acceleration as the car slowly began rolling and continued to accelerate to a normal speed but at much higher rpm. I took it to the dealer and they said that is was stuck in second gear. Park and reverse also worked but none of the other forward gears worked manual shifting the transmission or setting at any other drive position. They said they fixed it because of a service bulltin put out by gm. They told me they fixed a wiring harness, replaced the ignition switch and cleared all the codes.