New to forum transmission issue

[dsmxjb]

Hey, New to the forum and to these cars. I have a 04 Grand Pirx GTP with about 120k on the clock. It's been a great daily driver for a while now but its started having a issue. Just normal driving it started having a issue with the transmission. It feels like it is slipping during take off but it drives fine when it gets to speed. Now this only happens in D. When the car is in manual mode it drives just fine. Since this has started happening the car has been parked and I've been driving my other car. I took this one to the transmission shop and they told me it needed rebuilt or replaced. That brings me to my question which transmissions are compatible with this car. Can I only use a GTP transmission or will any Grand Prix transmission work? I'd really like to get this car going again. Thank you for any help.

[Fivefingerdeathpunch]

Look up triple edge performance, they have a common problems page that might show some light on the issue.


If you found a used transmission you'd need to fine another 2004-2005 GTP transmission or a 2006-2007 supercharged GT transmission. GTP's use a different gear ratio and that's why they need to match to be a direct drop in swap. 2004-2005 base models and GT's use a different gear ratio.

And COMP G transmission have a different gear ratio compared to the regular GTP's.

Base = 3.05's
GTP = 2.93's
COMP G - 3.29's.

06-07 GT = 2.93's.

[WarStryker13]

It doesn't need a full rebuild in order to drive like normal, but it will need some parts.

Sounds like the input clutch piston/seal, it's a pretty common problem. The bandaid for it would be some Lucas stop slip and a Trans-go shift kit, it usually works really well.... but it might not eliminate the problem completely.

The replacement trans would have to be out of an 04+ GTP, the previous years of GTPs had a different valve body and controls, and the non supercharged have different gearing, differentials and axles.

Someone else on here will probably have a better idea of what your best choice will be.

Edit: you said it has a manual mode? Tap-shift? If so, you've got a Comp-G...

[dsmxjb]

Thank you for the company name I will check it out.

Thanks for the info on the transmissions that really helps a lot. Now I know what I'm looking for.

Thank you for the info on the band aide fix. I'll look into that too it's been difficult looking for a gtp transmission. I've can find regular grand prix all day long for parts. That's what got me wondering if I could use one of those.

Yes, I have manual mode which the car drives perfectly fine in. It's just drive that doesn't work right. I'm not driving it at all though right now I cant imagine it being good for it to drive it right now.

So when finding a used transmission it needs to be another 04+ GTP with manual mode which is a Comp G?

[J57ltr]

If you have tap shift (gear selector does NOT have D,3,2,1 but does have D and M) then you need a transmission out of a Comp G or another GTP with the Tapshift option. Tap shift has the paddles on the steering wheel to shift up or down.

Unfortunately they are like hens teeth.

Jeff

[WarStryker13]

Mine's had that problem for years, the bandaid helps but mine is still slipping, I'll rev it slightly and it will "thump" into gear and go... Still running, but I've already got plans for rebuilding it.

IIRC it's due to the seal leaking, requiring more pressure to close the input clutch. That's probably why the manual mode works better, because of the higher pressures.

[rickisrad]

You will need a 4t65E transmission for a Comp G with the 3.29 gears and tap shift. Very common issue with these transmissions. Like WarStryker mine did it for years before I replaced the transmission. The Transgo and Lucas additive helped but it still slipped, a good word I read somewhere is "delayed engagement". I like taking off fast and didn't want it to break on me so I replaced it. For normal driving it will probably have lasted for many more years.

You can try to run some Trans Tune cleaner (white and red can) for a few weeks to clean everything out then do the Transgo shift kit and Lucas additive. The trans tune helps clean some of the gunk off the sensors. From what I've read it may start with a sensor or solenoid being covered in soot then leads to valve body and or clutch damage. Since these issues go away while using tap shift another option would be to get the trans line pressure raised more than normal in the pcm as well as the above "fix".

[hotdogstand]

If it's just a valve or piston, you likely can replace just the valve body rather than the whole trans. I certainly can't elaborate any more to say whether there are VB differences between tapshift and non-tapshift models, but a cam suggest a google search, and a search of these forums, for that answer. A complete valve body will likely only set you back $30-50 from a wrecker, vs couple hundred (and a half day of your labor) for the whole trans.