I have a 1992 GMC C3500 with a 6.2 liter diesel 2 wheel drive. I bought it about 3 months ago from a local repair shop, the mechanic said that it was brought in for transmission work and he replaced it with a used tranny. It worked great for about 2 months, now it shifts hard into second gear but will not shift into 3,4,5 or OD. I live in the mountains and used to only have this shift problem leaving the mountains. When I get to town at the bottom of the mountain, the problem would go away. Now it is all the time. it has 265,895 miles on engine. The fluid is redish brown in color. I did not want to do anything until I got some info on what to do.

 

Sounds like a rebuild is in store for you but first I'd do a tranny fluid and filter change, take note on if you see chunks of metal in the tranny pan around your magnet. If so you'll have to have it rebuilt. Probably not the news you wanted to hear, sorry.

 

Thank you for your help.