My daughter has a Grand Prix 2004 GTP, and we just had a rebuilt transmission installed at about 122,000 miles. As I drove it home, it seemed like the engine was running a little higher RPM for the speed, which might mean it was either not going into 4th gear, or it was but the torque converter lock-up clutch is not engaging.
If any of you have a GTP of this model year, could you please check what the engine RPM is at 60 MPH after the car reaches that steady speed, and report back here? On her car it is about 1,700 rpm, which seems faster than normal, but I haven't driven the car regularly for a long time.
To make this comparison valid, you must be driving the supercharged GTP, because that has the 4T65E-HD transmission. That transmission has a different ratio than those used in other models of the Grand Prix that year.
I realize that another possibility might be if they had gotten the wrong transmission installed, but that would have dropped the rpm, not raised it. I also discussed that with the owner of the shop before he did the exchange, who understood the importance of getting the right tranny in. Plus if it had been wrong, I'd be getting a check engine light by now, as the wrong tranny sets off alarms in the ECM, and that hasn't happened.
Thanks in advance for your help,
Terry
