One problem related to transmission stuck in gear has been reported for the 2003 GMC Envoy. The most recently reported issues are listed below.
First problem occurred in 2008, driving to work in 2003 GMC Envoy slt (original owner) heard clunking noise when downshifting. Took car in to shop for repair (just over 50k miles so out of warranty). Shop explained that the transmission needed to be replaced $4000 with one year warranty. Since I was planning on driving cross country decided to do the repair. One year later, driving and trying to accelerate on a ramp to find SUV stuck in second gear and wouldn't accelerate while rpm kept going up. Also heard clunking when downshifting. Pulled over and tried to get gears to shift by slowing down and speeding up (to get rpm to drop). Drove car to dealer who stated I needed a new transmission (again). Dealer removed transmission and "found input bushing in pump bad. And reverse drum. And had heavy metal contamination". When asked why this is my third transmission in six years the service agent said "bad luck". Both replacement transmissions were rebuilds. The current transmission is not under warranty.