2004 envoy slt xl

and new to this site, need alittle help, anyone else having problems with the speedometer, thought the dealership fixed it but sure enough this past week it freezes up at different speeds again,( 70, 55,) will lock up in that speed, and stay in that speed until i turn the vehicle off, than when i restart it the speedometer goes down around 10 mph each time i turn the car on, sometimes it will stay at 70 mph and when i drive it actually works from that speed , was going 120 + the other day, LOL, any help would be appreciated, is there a cable or some type of electrical system involved, thanks mike

Had the same problem and the dealership is fixing it now, it needed a new cluster. My friend had the same problem with his.