Thread: No 2 to 3 shift until HOT

The 97 GTs have the 4T60E transmission but are similar internally. There are a few things that can cause your problem and there really isnt anything that is going to be an easy fix. The first thing you should do is check fluid with the car warmed up and running in park. After this is verified then you need to get ahold of a scan tool or take your car to someone or a shop who has one and verify that the pcm/computer is commanding the shift as this transmission's shifts are electronically controlled. On the outside of the transmission case there is a vacuum modulator on the top front side of the transmission that has a vacuum line plugged into it. Make sure the vacuum line is still attached ok and then remove it right on the modulator and make sure that there is no transmission fluid inside the tube. If there is then the modulator will need replaced. After that has been checked out and if it appears ok then you are left with internal problems. There is a lip seal that seals the 3rd clutch piston and is known to cause this. There is an updated aftermarket seal that is made by Transgo that addresses this problem. There are a handful of other seals that can cause pressure loss for 3rd gear also. Since you mention it shifts hard when it does shift after it heats up this could lead you to a valve body problem.

97 only GTs came with the 4T60E, only the GTP that year had the 4T65E and all 98+ GT/GTPs came with the 4T65E. The easiest way to tell is by looking at the top side of the trans under the throttle body of the engine. Straight down from there on the side of the trans pointing towards the front of the car you will see a small metal can with a vacuum line going to it. It will be grey in color and a few inches long and round if the original, or it will be smaller and gold in color if it has been replaced. If it is a 4T65E then there will not be a vacuum modulator and the electrically connector will be at the very top of the side cover of the trans just under the intake tube.