Thread: 05 Comp G Won't Shift to 3rd under 40 MPH

Hello I have a 2005 Grand Prix Comp G with Tapshift. I purchased it recently and it has behaved this way from day one. At any throttle position the transmission refuses to shift from second into third under 40mph. Rev it up just to 40 and it pops into 3rd. Drop down little bit under 40 and it downshifts back to second. When I use the manual mode to tell it to go to 3rd gear it makes no difference. However, when I use the manual mode to tell it to go to 4th it will shift into 3rd above 25 or so as it should. I would say it shifts a little harder than I feel like it should, but other than this I have not noticed any other problems. No slipping, shuddering, hesitation, etc. Fluid level is correct, fluid does not appear burned or smell strange. My only guess at this point is the pressure control solenoid is stuck in 'high pressure' mode, but that is really a completely shot in the dark. Any idea what might cause this?

You know I thought about that, though I forgot to mention it in my post. I just can't fathom why someone would tune it to do that? The answer is I don't know if it has been tuned, and it has a couple little mods to it that might be consistent with a someone tuning it. What would be my best bet for getting it checked/flashing it back to stock?

Have the dealer flash it