Thread: Slip and Harsh shift '04 GTP

The transmission in my daughter's 2004 GTP with about 122,000 miles is acting up. The behavior is pretty consistent. When the car is first driven (cold), the 1-2 shift sounds like it is slipping (engine revs up a little, then pulls back down), even when it is not hard acceleration. Then the 2-3 shift is harsh, like a clunk. Other shifts are not noticeably bad.

As the car warms up, the bad shift behavior goes away, and the car shifts normally.

After it cools down, it repeats the behavior.

I've tried a few easy things:

Check oil level, okay.
Work the shift lever through the gears with car stationary and engine running, might have helped for short time, but problem comes back pretty quickly.
Unhooked battery for an hour to reset the computer. No benefit.

I've ordered an OBD code reader that should read tranny codes, will be here in a week or so.

Does anyone recognize this behavior as a specific problem (brief slippage of 1-2 shift, harsher than normal 2-3 shift, both when oil is not up to operating temperature)?


Also, does anyone know if the "HD" version of the 4T65E goes with the supercharged higher horsepower GTP, or is that used elsewhere?


Thanks for any help

Terry

Originally Posted by Fivefingerdeathpunch

The 4T65e HD is the only transmission that was put in the supercharged and V8 GXP cars. The 4T65e which is exactly same minus the gear ratio and HD diff are in the regular SE, GT, Base model cars. The HD transmission is not any stronger than the regular transmission but to be a direct drop in replacement you need a 2004-2007 GTP/GT(supercharged 06-07) unit to work, if you went that route. Also the COMP G transmission run a different gear ratio as well compared to the standard GTP cars, another small change GM did.

Thanks for the link to the site. That might help when I get the codes out.

Your comment on the HD transmission needing to be used in the GTP is also helpful. Just checking what I might do, I went to two auto parts places to price a remanufactured trans. At least one of them had both an HD and non-HD transmission shown as appropriate for my GTP. What a disaster it would be to pay to have the wrong one installed.

Terry

Does he have to have the same trans code off the tag to use a different trans?

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I was told and spent countless hours that the codes on the pin from the side of the trans have to match, but I could have gotten misled. I found one almost 150 miles from my place and I had to pull it 😔. I went to a few junk yards to look for one. I'm not saying your wrong I was asking your advice.

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