I purchased this 07 GXP brand new, and have always had a 1st gear slipping issue from a dead stop. All other gear shifts are fine. The unit is still under a GMPP Major Guard warranty for another year.
When I'm at a stop, I'll take my foot off the brake and accelerate (fast or slow doesn't matter) and every once in awhile it'll move slowly forward, like it's only getting about 1/4 power, and then the transmission will thump into gear and jerk the car forward. It's gotten to the point where I can feel the car isn't moving ahead with the amount of gas I'm giving it, so I'll let off the gas for a moment and re-accelerate and everything is fine. No violent thumping. In the last few months it's gotten worse. Several times now I'll be rolling up to a red light, and almost come to a stop when the light turns green. When I go to accelerate, it slips. The slip time ranges from an instant to between 1-2 seconds (an eternity).
It used to be months between the slipping, but as the years have gone by it's gotten worse. I've had it into the dealership at least 3 times now, with the first time being early on when I had the car. It happened so infrequently, they couldn't do anything because they couldn't reproduce it. Then a year or two ago it happened several times in one day and I brought it there the next day. Naturally, they could still never reproduce it. Fast forward a year or so and I take it in again, since I had another issue where the headlights started going off without warning. So I had them look at the transmission again while it was there. They topped off the fluid, found a leaking fitting and replaced it, and sent me on my way. It didn't slip for about 2 weeks or so after that trip (and it had been slipping every other day or so) and I thought it actually was fixed. Unfortunately, it started slipping and has been almost every day (it's worse during the fall/winter when it's cold). The slipping happens in a ratio of once every 20-30 times I accelerate. Sometimes, though, it'll go a day or two with no slipping. It's odd. Last week my wife got fed up and took it in again. They still couldn't get it to happen, and found 2 crushed motor mounts, and replaced them and said that was it. Took a couple days after getting it back and it slipped again.
They mentioned if the mounts didn't resolve it, they'd likely have to tear into the transmission to find out what's up. They sounded reluctant, maybe because it's under warranty and they have to justify it without reproducing it? I don't know but it's like they were trying to talk me out of it. Maybe they think they'll have my car out of commission for weeks/months or something?
Is there anything they can look at that doesn't require ripping into the transmission? Or is that the only way? I've read about a few issues on here, which sound pretty similar to my issue. I'd like to try to gather up some information and bring it to them in case I get some sort of resistance in them wanting to fix this. I thought about driving around with them and trying to make it happen, but there's been days where it just doesn't happen.
Naturally I'd like to get this done while I still have a warranty, and still have plenty of time left on the warranty in case their "fix" doesn't work.
Originally Posted by Pinch
