Tranny Question?

I have a 1996 Grand Am 2.4L It Has about 170,000 on it. But I think that there is a problem with the Transmission or something. When You get in the car start it up and put it in reverse, the gear shifter will be in reverse, and it will start to move but then immediately stop hard, almost like it's in park again but it's not. Any Ideas to what this could be? Also to actually back up you have to hold the gear shifter like between R and N just to back the car up.

Sounds like an out of whack linkage, stretched or out of adjustment perhaps. Not sure on these if the detent is located within the trans or outside of it since it sounds like your are holding it out of the r and n detent positions. If it detents between r and n then I'd say the linkage is out of adjustment otherwise (unless the detent mechanism is external from the trans) I'd say the problem is within the trans.