ive got a 2000 grand prix gtp 2 weeks ago it started to slip real bad and whin out the blue so right away i changed the fluid and filter it drove fine for 2 week and now it is doing it again, it whines in all gears even at idle, the last time i drove it it slip so bad that it was moving at all, i turned the key off and started back up not even a second later it drove fine after that for a couple of miles and started to do it again, it is also pulling a torqe converter stall code or something like that what could it b ? should some additive work? or just replace the tranny?
