Two problems related to transmission failure have been reported for the 2003 GMC Envoy. The most recently reported issues are listed below.
The transmission failed in my 2003 GMC Envoy with approx 95,000 miles. While driving down the road I went to pass a slow moving vehicle. As the transmission down shifted there was a "bang" so I pulled over to look under the truck, and made sure nothing had fallen off. I got back in the s. U. V. And made my way back home with no problem. The next day when I went to back out of my drive way there was no reverse. I called a local gm dealership and was told that the problem appears to the sunshell gear. According to multiple post online, seems to be a common failure among Envoy's and trailblazer. I checked the fluid and it appears to be fine, not low, not burnt, and still red and clean.
The transmission failed in my 2003 GMC Envoy with 82,000 miles. The problem appears to the sunshell gear which seems to be a common failure with this transmission. Because the transmission was downshifting hard, I took the car to a GMC dealer less than 1000 miles ago to have the transmission looked at. I was told my the dealer that there was a problem but not to worry about it. Now the transmission has no reverse and the repair estimate is $1,800.