I need help trying to figure out what is wrong with my 1999 Blazer. Let me explain what happened. i was driving down the road at 55 mph, then all of a sudden it felt like someone came up behind me and hit me and at the same time it felt like I had my foot on the brake. I pulled over and stopped and called for a trailer to load it up and take it home. We were able to drive it up on the trailer but after we got it home it would not go forward, only backwards. We have put in another transfer case (used) and it is doing the same thing. I'm about to give up and junk it. But before all this happened, I had to have a heater core put in it. The guy took the whole dash out, I mean everything!!!! Does anyone have any clue? Please HELP!!!!!! Thank you in advance!!!!

 

ive seen transmissions go bad that would cause that. had a old 80s truck that was locked up in reverse. might have melted the clutches together or something