Yesterday, as I was backing out of a parking space, I put my 98 blazer in reverse and put my foot on the gas. As I pressed down, all it did was rev the engine, like it was in neutral, but it was in reverse. My bf suggested maybe it didn't shift completely into reverse. So I put it back in park and shifted again and it shifted fine. So today, I went to put it into reverse and the same thing happened. This time I lightly moved the shifter to see if that was the case but it didn't move, so I put it in neutral then to reverse and it was ok.

I'm wondering what this could be? I'm gonna take it in to my mechanic next week but does anyone have a clue about what this sounds like?

 

Could be the shift cable out of adjustment.