i was driving my 92 c1500 and had no problems with the transmission the whole year i had it. came home from work and had to go to the store and while i was leaving the store the truck shifts into 1st and 2nd fine and right before it shifts into 3rd i take my foot of the gas and it shifts anyways but really hard and loud and now ever since then it wont shift into reverse and sounds like its stuck in a single gear and wont shift passed it. it has a 4l60e with a 262 4.3l v6 tbi.

 

welcome to the forums

 

Usually when a truck or car has issues with the transmission and still is drivable, the problem could be with the shift solenoids or valve body. By taking it from small to big I would check the easy stuff and go from there. But if there's no ugly noise or sound while driving it then some sensor is bad. When something is serious then it would be the reverse drum or governor and truck won't move...