Hello folks, new member here.

I recently purchased a 1991 Grand Prix with a recently rebuilt tranny.

I am finding that the tranny slips from drive and overdrive into neutral, when the car is stopped. It doesn't do this every time. When I manually shift into neutral and then back down into overdrive or drive, I can move again.

Aside from that glitch, the transmission seems to be running nice and smooth.

The car had very little tranny fluid when I bought it, and I topped it off with clean fluid (no flush). I just checked it again today and the fluid level is still good.

Any other suggestions?

Have you checked to see if the shift linkage is adjusted correctly?