How do I know if my transmission is bad or if it is something else? 2003 GT w/ 3.8

[jevanz]

I have a 2003 Pontiac Grand Prix GT with a 3.8 liter engine, 170k miles. I have been experiencing transmission issues. When the car is cold, and I begin to accelerate, it wants to stay in first gear. If I let off of the accelerator, it will eventually shift into second and then will drive fine. Initially this occurred intermittently but this is now occurring more frequently. Yesterday, I was in second gear and tried to accelerate and the rpms revved up and it would not shift until I let off the gas. Can anyone please help me to determine is I have a faulty transmission, or if it may be something smaller like the tranny control solenoid?

I have found a used transmission with 72k miles on it for $425. I hate to swap that out, only to find that the issue was something more minor. Thanks in advance for your help.

-Jason

[blueguy]

Sounds like a little slipage.

Hopefully you haven't flushed it...

If not, don't do it yet; Just do a simple pan drop, filter change, and refill with 8~ quarts of new fluid....add some Lucas Stopslip in there too. I'd also check the fluid level as of now. If it's low or smells burnt...then I'd be worried.

[dsmuts]

If you do swap the trans you need one out of an 03 gt only