Strange feeling

[Plasboy]

We were out last night and the car made a strange action. Slowed from 65 by ten or 15 mph to let a car in front turn. Didn’t hit the brakes just coasted down. When I accelerated it seemed as if the car started to speed up then it jerked twice, no noise, then just went on. It’s done it before. Guessing it must be the transmission. Any ideas or similar experiences.

TIA, Joe

[JB]

Obviously it’s hard to interpret on the internet. Remember these machines are never perfect as surprising as that is to most people. I assume you’ve had the car serviced appropriately. You can call OnStar by pushing the button in the car and they will give you if you ask for a complementary disagnostic code if one was set. These cars are extremely integrated and if anything goes wrong it should set a code.

tell OnStar to email you the code.

then call the dealership to make an appointment if a code was set. If not then just enjoy your ride.

sometimes the dct is caught out of step. It’s rare but in almost 25k miles it can happen occasional without anything to worry about.

I hope this helps.

like I mentioned push the OnStar button and ask for a complimentary diagnostic report. They will be able to see if a code was set.

don’t worry. I’m guessing it’s nothing to worry about yet that would be my first course of action.

[topfuelman]

See if you can repeat the problem; were you accelerating hard after slowing down? May just be the computer trying to determine which gear you should be in based on throttle position. This may be a normal condition as you're not dealing with a "normal" torque converter automatic transmission. This is a dual-clutch transmission (much like 2 manual transmissions put together) and shift feel will be different as well. Is there any loss in drivability associated with this? Are any DTC's set? How many miles on it? Is software up to date? Has car always responded this way when in similar conditions? Try putting in Manual mode and repeat same conditions; does the car respond differently when you shift for yourself?

[socarate]

I agree with JB. I've got nearly 25k on mine and I have occasionally felt a bit of jerking from the transmission since I've had it. Mainly at lower speeds. I have always attributed it to the DCT having trouble deciding on a gear at low speeds. I've never had an error message or any issue come up at regular services

[Plasboy]

As I said it has done it a couple of times before. It has recently had an oil and filter change and DCT flush and filter at 3600 miles. Updates are current as far as I can tell. Don’t know if dealer checked for codes. Car operates perfectly otherwise. I’ll check for codes, thanks for the advice.

[davec81]

That sounds right. The DCT will always try to have the next gear engaged.

If you are accelerating, it will have the next higher gear engaged on the alternate clutch.

If you are decelerating, it will have the next lower gear gear engaged.

If it thinks you are accelerating and engages a higher gear, but you actually decelerate, it will have to switch gears on the fly, possibly causing the jerking.

Sounds like you were decelerating and the DCT was prepared to move to a lower gear, it jerked when it realized you wanted to accelerate and then had to switch two gears.

[JB]

That sounds right. The DCT will always try to have the next gear engaged.

If you are accelerating, it will have the next higher gear engaged on the alternate clutch.

If you are decelerating, it will have the next lower gear gear engaged.

If it thinks you are accelerating and engages a higher gear, but you actually decelerate, it will have to switch gears on the fly, possibly causing the jerking.

Sounds like you were decelerating and the DCT was prepared to move to a lower gear, it jerked when it realized you wanted to accelerate and then had to switch two gears.

This sounds very likely as described above.

[Plasboy]

That sounds right. The DCT will always try to have the next gear engaged.

If you are accelerating, it will have the next higher gear engaged on the alternate clutch.

If you are decelerating, it will have the next lower gear gear engaged.

If it thinks you are accelerating and engages a higher gear, but you actually decelerate, it will have to switch gears on the fly, possibly causing the jerking.

Sounds like you were decelerating and the DCT was prepared to move to a lower gear, it jerked when it realized you wanted to accelerate and then had to switch two gears.

Sounds like a likely scenario. Kinda thought of that but wanted an opinion. Thanks for the input.