2007 Pontiac Grand Prix - transmission jumps

Transmission jumps when taking off.

Is that good? Or is that bad? You don’t say.

Post back and ask a question and we’ll try and help.

It feels different now than when it was working correctly, right? So explain more clearly how it feels now compared to then.

The other day went out started the car let it warm up for about 2 minutes pulled 2 the end of my driveway stopped as I began to accelerate it’s like it came out of gear or something motor raced a little bit and then all the sudden it went into gear kind of hard that time. Another time I was coming back from Cincinnati got off the interstate pulled up 2 a red light went to take off and was like it wasn’t even in gear and then all the sudden went into gear kind of hard. It does it so fast by the time you realize what it’s did it’s already did it I know that might be the cause of the front seal coming out twice within a year I’m not sure are they some kind of sensor that shifts the transmission that might B going bad.

Sonhave you checked the fluid level? Low fluid will cause that symptom. Considering the front seal came out, twice, there might be a leak. If it is the front seal again, I would say you are in need of a new transmission since there should not be high pressure being applied to that seal.


Yes I always keep check on tranny fluid and oil. I think the tranny shop put the first seal in crooked. Also when im on a trip and run into really slow traffic when the tranny is hot it will shift hard untill i get back up to speed and it cools… doesnt do that around town though…

Are they a shifting censor for the tranny on this yr car…

No. There is a transmission temperature sensor and that’s all I can see on Rockauto.

I’m assuming this is a conventional automatic, not a CVT. From your description it sounds like either the clutches or bands inside the transmission are slipping. During a shift some bands and clutches release, and others engage. Releasing is no problem, but it takes a really strong force (i.e. high fluid pressure) to fully engage & not slip. That force comes from a hydraulic fluid pump inside the transmission, and from spring loaded hydraulic valves that push on the engagement actuators, often triggered by electronic solenoids. Both the pump and the valves have seals, and if those seals harden they leak and aren’t able to develop the pressure needed to fully engage the bands and clutches. If the transmission fluid level is low or the bands and clutches are plumb wore out, or there’s a solenoid failure, the same thing will happen. A transmission shop should be able to check the pump’s output pressure, and measure the pressure at some of the intermediate points. That’s where to start w/this sort of problem, presuming the transmission fluid is in good condition and at the proper level.

Transmission went out and had it rebuilt at 102k. Has has 240 on it now. Fluid is and has been changed multiple times…

I can’t vouch for this product myself, never tried it. And it may not be compatible with that particular trans. But some of the experts here recommend to try the Lucas transmission fluid additive for this sort of problem. It supposedly softens hardened seals inside the transmission. That may boost the fluid pressure to the clutch and band actuators. I don’t think this is considered a solution per se, but something that can bide time until you can get a proper solution, which is probably another rebuild.

I appreciate the advice…