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Need some suggestions

F

fatjoe

New member
First of all i want to say thanks for all the help that i have got off these threads. I currenlty bought a 99 grand prix gt when i buying it i knew the tranny was going. So i ran some seafoam thru it then serviced it. I got about 600 miles on it then the problem that alot of people have, it started to not go out of 2nd gear. Any ways my question is i bought a 01 bonneville for a tranny, i know that the 99 is is one year only but we wanted to see if we could get it to work. So we tore both apart in all we could find is the plug was different in the neutral safety switch was on the inside of the new tranny. So we put the wiring harness from the old one on the new one in switch the switches. Got it back in and now the only problem i have is very little rpm change at shifting. so im wondering if someone could give it a thought in see if they could come up with a solution.
 


Did you check to see if the gear ratios were the same? Are you using the same torque converter or the one from the different transmission? If you installed a transmission with a lower gear ratio ie..... your GT came with a 3.29 overall ratio, and if you installed a transmission with a 3.05, 2.93, or 2.86 ratio then the torque converter will be working harder during each shift and the rpms wont noticably drop as much as with the 3.29 gear. Do you have the ID tag codes from each trans? I added a link to my website to find the ID code if you want to check
 
Okay i looked into it and it does have 3.05 gears. We did use the torqe converter out of the new tranny. when i asked a buddy about he said something about taking it to a dealer to get the pcm cleared think this would help?
 
If the pcm wasnt reprogrammed for the 3.05 gear ratio then there are going to be problems and the pcm will throw an incorrect gear ratio code and this causes rough shifts and odd tcc behavior. In your favor the gear ratio can be changed by using the differential out of your GT transmission in the new trans as long as it is still in good usable condition and that will take care of your gear ratio problem and may also help with how it feels but likely the trans you put in has a torque converter with a different stall speed than your original one and is making it feel a bit looser and you are seeing the rpm change not as much as before during the shifts.
 
Okay thanks. I am goin to do that. If it throws an incorrect gear ratio code will i be stopped in my tracks?
 
It will throw that code if the ratio is different than what the pcm is set up for. It takes a few shift cycles for it to recognize this.
 


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