I have a 2007 Chevy Impala with the 3.9L. It has just over 110,000 miles on it. I’ve owned the car for about 5.5 years. Back in 2012, I took the car to a local transmission shop. Here’s the reason: Let’s say the car has sat overnight. I start it up (regardless of the season) and go to the stop sign at the end of my street. When I go to accelerate, there will be a very short lapse and the car will seem to jerk into gear then go. This is a very intermittent problem and does not happen every day. The car will do this for a bit when accelerating from a dead stop and then the problem goes away.
The trans shop said the transmission needed to be rebuilt. Guy told me they’ve seen problems with the Impala transmissions and, if I remember correctly, that the parts used inside aren’t the best. Looking for a second opinion, I took the car to a Chevy dealer. The dealer was not able to experience the jerking. I had the trans service done (80,000 miles at the time). The problem persists to this day and has not, thankfully, noticeably gotten worse. I decided to take the car to another dealer last week. Same thing: the dealer could not create the jerking issue. Again, this issue is very intermittent.
I am not sure what to think or do at this point. I called a couple shops around town and have gotten the following advice/information:
Bring it in and we can see if we can recreate it, but can’t guarantee it.
The transmission needs to be rebuilt (this without even looking at the car).
Wait for the problem to get worse so that it CAN be diagnosed properly.
One guy said he didn’t trust the dealer mechanics, that they “just drive around the block once.” I am not sure what to do and would appreciate any help or suggestions. Thank you.
When I go to accelerate, there will be a very short lapse and the car will seem to jerk into gear then go.
During this “lapse”, is the engine revving up as you push on the gas? If it is, it sounds like a sticking valve in the transmission. If not, it sounds like the engine itself is balking.
When this symptom started with my Ford truck, it was not long, a month or two max, before the truck was in the transmission shop for an auto transmission rebuild job. At first it only happened on cold days, before the engine was warmed up. Automatic transmissions have clutches, and those can wear out and start to slip. And the valve body (sort of a mechanical hydraulic computer with all sorts of passages and gizmos) can get plugged up with gunk, which causes the control valves to malfunction as mentioned above. A rebuild fixes both those problems. I think that’s what you are looking at.
Start asking around at auto shops you know for who’s the best inde transmission shop in town. No harm done to take your car there and have them do a test drive. They might ask you to leave it there for a few days, to see if the can get it to repeat the problem.
@insight: Thinking about this, I don’t think the engine revs right before the jerking feeling.
@GeorgeSanJose: I’ve been experiencing this for almost three years. As I mentioned in the original post, the problem, thankfully, does not seem to have gotten worse. I did take it a local trans shop back in 2012 and I was told it needed rebuilt. I went to the dealer for a second opinion and they could not replicate the problem.
It’s odd that it hasn’t gotten worse. That’s one argument in favor of waiting I suppose. In my case, the way it started, I’d pull away from a stop sign on the first drive of the day, and sometimes the engine would rev but the car wouldn’t move. It was very clear the engine was reving when this happened. I’d let it idle a few seconds, try again, then it would move ok. To address it, I changed the fluid and replaced the transmission filter. After a couple of months it was clear the problem wasn’t getting any better, and in fact was getting slightly worse week by week. So off to the transmission shop for a rebuild, which cured the symptoms straight away.
If your engine doesn’t rev just before it goes into gear, well I’ve had a symptom like that too, again on my Ford truck. Several times in fact. I’d call it a “hick-up”, where the engine seems to gasp a bit – definitely doesn’t rev – before taking off from a stop. It sort of feels a little like the transmission might be jerking. But it feels more like a problem with the engine. In fact if I pressed too hard on the gas the engine would outright stall.
This problem in every case was caused by a vacuum leak. A vacuum hose had split, or a vacuum connector had fallen off, or what was usually the cause, a vacuum controlled device developed a diaphragm leak. In my truck’s case it was usually the device that operated a little door in the air cleaner ass’y that allows warm air heated by the exhaust manifold into the engine when the engine coolant was cold. The “gasp” symptom wasn’t caused b/c that device wasn’t doing its job of routing the air, although that probably didn’t help, it was caused b/c the leaky diaphragm was allowing unmetered air into the intake manifold, leaning out the mixture. Replacing that device always fixed this problem.
Ask your shop to check the vacuum system.