Hi All
This is my first post... I have owned my Grand Prix GT "40th Anniversary" since new... I have loved every moment.
Currently I am working towards modifying the car to be a better performing daily driver. To start my modifications I have replaced the stock 4T65E transmission with a performance 4T65E-HD transmission in preparation for a turbo install some time next year. Anyways the new transmission was installed by a respected transmission builder... but there are issues with hard shifting or not shifting correctly under WOT. Below is a list of issues I have encountered...
1. Shifts hard through all gear shifts.
2. Under WOT, shifting from 1-2... car hits 6000rpms and then jumps a couple of times before shifting. Seems like a rev limiter engages before the actual shift occurs.
3. Under WOT, shifting from 2-3... car will not shift unless I pull up on the accelerater. At 6000rpms it seems like a rev limiter engage again (car jumps) but it will not shift until I pull up on the accelerater.
My transmission installer has checked the transmission over and according to him everything is in good working order with regards to the mechanicals of the transmission. He believes the PCM is the problem. He tells me that the maintained transmission pressure is high at park, "current out of the PCM is sitting at 0.12 to the EPC solenoid, which means high pressure" He says that as the car is put into drive the current jumps up to .88, but then returns to 0.12 and maintains the high pressure.
The question is... is it likely that I have a PCM problem or is it likely it is something else?