99 GTP - Overdrive at 37-38mph

[goldberg_52403]

Hi all,
I have a 99 GTP with a known transmission issue, the RPM surges while in OD under light acceleration. I do notice that it shifts to OD early, around 37-38mph and maybe even a little lower. Would anybody have an idea of what would cause this?

Thanks and Happy New Year!

[BNaylor]

It would help to post your mileage. Also, what steps have been taken to date since this appears to be a prior posted problem and most likely TCC related.

Best to get it scanned with a trans capable scanner and see if any DTCs are stored. Many do not trigger the SES/CEL light.

[goldberg_52403]

The car has just about 106k. I have posted before in regards to the fishbite effect while in overdrive, although I havent been able to get the tranny scanned yet. This post was aimed more at the car shifting into OD seemingly early, although I suppose the issues are related. I will try to get the car scanned tomorrow.

Thanks BNaylor.

[BNaylor]

Just so we know some history here is your old thread going back to August '07.

http://www.automotiveforums.com/vbul...d.php?t=745684

I'd say there is a relationship between the two. Is the SES/CEL light still on? The TCC circuits or any problem in that area could affect 4th - OD. OD is coming in earlier than it should but at least you're not dead in the water. You might get better fuel economy with the early shifting. If its annoying you can override by keeping it 3rd gear and then shift manually to OD at higher speeds - over 45 mph.

When was the last tranny service, ATF and screen filter? And are you sure the TCC fishbite is not a secondary ignition problem like plugs, wires, coils? Hopefully the scan reveals something.

[goldberg_52403]

Ok, I just got back from the transmission shop and unfortunately no tranny codes showed up on the scanner. Currently there is no CEL/SES light, the dealer took care of that issue by "fixing a wire to the TCC". I also had the car re-scanned after the fix, just to double check, and nothing came back as well. Thats a good point about holding it in 3rd until OD is needed, didnt think of that. As for any transmission maintenance, I have not had anything performed at this time.

Not too long ago, I did put in new NGK TR55IX plugs although the stock wires are still there. I thought that I tracked the fishbite issue down to a faulty TCC solenoid, but I cannot be sure. I also thought it may be the TPS, although the earlier gears run smooth.

I am considering a tranny filter change/flush, replacing the TPS, and new plug wires. Would this be a good idea?

Thanks for all the help once again.