DCT severe jerking / rocking the car

[rblood303]

so, my mate wants an M3, we went to test drive a dealer demo, and shortly after a few minutes into the test drive, we were coasting (he could have lightly applied the brake), the gearbox automatically shifted into 3rd gear, and the car starting jerking like mad and there was some clunking. mate applied the brakes and then came to a stop and didn't feel it again for a while.

now owning an M3 myself, while the others didn't really notice anything, i noticed it immediately.

anyways after 2 minutes, again while coasting to a stop, it happened again so i quickly told my friend to accelerate slightly then let go, and the jerking continued, the car was in 3rd gear. it happened for a few seconds and we had to come to a stop. i asked the sales guy if this was normal, and to be honest i don't know why i was expecting a different answer, he said that it was.

after that i didn't happen again but it really concerned me and i want to talk my mate out of buying it

is this something that anyone else has experienced? if so could this be a major problem?

the car has warranty but just don't want him to go through the something avoidable.

thanks

[SinatraM]

i have a 2015 dct. its a dct its gonna jerk sometimes. bmw even has a video on youtube addressing the dct (

)

[CigarPundit]

It is possible to induce bucking with the DCT, just like with any other manual transmission. The M3 is a powerful car with lots of low end torque, and first and second gear are a bit on the short side, IMO. The combination of these things can result in pretty severe bucking in first and second if the throttle is not managed correctly. That said, although I have induced bucking a few times in first and second, I have never done it in third. It’s hard to know what happened from your description, but my guess would be user error, TBH. There’s nothing about the DCT that would throw the car into a violent bucking episode while trailing the brakes or coasting from third to second during a DCT commanded downshift (meaning, one that was automatically commanded in Sequential mode because the driver let the RPMs drop too low without downshifting, or one that happened in Drive mode). I can’t tell if you were in S or D mode from your description, but in S mode it will auto downshift at 1000-1500 RPM so that you don’t stall the car. Either way, coasting or braking in a low RPM downshift isn’t going to induce bucking.

[G35POPPEDMYCHERRY]

its so easy to buck this car....Unless YOU drive it and notice the same, then I would chalk it up to inexperience with the car

[ellipsis212]

Originally Posted by G35POPPEDMYCHERRY

its so easy to buck this car....Unless YOU drive it and notice the same, then I would chalk it up to inexperience with the car

100% agree. I thought there was something wrong with the throttle control and then I found out from this forum that it was my foot!

Try putting your entire foot on the pedal for finer modulation rather than letting your heel rest on the floor mat. FYI - this still happens on occasion when I hit bumpy pavement as I'm taking off in Sport Plus mode as it can rock the car just enough to induce a little chain reaction between pedal and foot.

[rblood303]

Originally Posted by CigarPundit

It is possible to induce bucking with the DCT, just like with any other manual transmission. The M3 is a powerful car with lots of low end torque, and first and second gear are a bit on the short side, IMO. The combination of these things can result in pretty severe bucking in first and second if the throttle is not managed correctly. That said, although I have induced bucking a few times in first and second, I have never done it in third. It’s hard to know what happened from your description, but my guess would be user error, TBH. There’s nothing about the DCT that would throw the car into a violent bucking episode while trailing the brakes or coasting from third to second during a DCT commanded downshift (meaning, one that was automatically commanded in Sequential mode because the driver let the RPMs drop too low without downshifting, or one that happened in Drive mode). I can’t tell if you were in S or D mode from your description, but in S mode it will auto downshift at 1000-1500 RPM so that you don’t stall the car. Either way, coasting or braking in a low RPM downshift isn’t going to induce bucking.

yeah i was definitely auto shifting. and was a smooth road so not sure what caused it. i'm even thinking that this was a m-performance school car and i don't know, could they have done something there that could have loosened up 3rd gear?

anyways thanks for the responses, unless this is normal behavior i'll just tell him to pass on this one

[G35POPPEDMYCHERRY]

Originally Posted by rblood303

yeah i was definitely auto shifting. and was a smooth road so not sure what caused it. i'm even thinking that this was a m-performance school car and i don't know, could they have done something there that could have loosened up 3rd gear?

anyways thanks for the responses, unless this is normal behavior i'll just tell him to pass on this one

def not normal behavior. could be reminients of a shitty tune...i mean theres plenty of cars so passing is not a problem. but if its desirble maybe u should give it a go

[rblood303]

Originally Posted by G35POPPEDMYCHERRY

def not normal behavior. could be reminients of a shitty tune...i mean theres plenty of cars so passing is not a problem. but if its desirble maybe u should give it a go

well being a dealer demo car, i doubt it could be a tune issue, unless it's a factory tune issue. but then again, the person who used the car could have tuned it lol

[G35POPPEDMYCHERRY]

Originally Posted by rblood303

well being a dealer demo car, i doubt it could be a tune issue, unless it's a factory tune issue. but then again, the person who used the car could have tuned it lol

oh missed that part. yeah i would balk

[MisterF80M3]

When I nearly floor the car on sports+ there is a severe kangaroo effect.

[rblood303]

Originally Posted by MisterF80M3

When I nearly floor the car on sports+ there is a severe kangaroo effect.

yeah i know what you mean and i've done this before but it didn't feel like this at all. the jerking was at much higher frequency like twice as fast, almost like shaking more so than jerking, and not as hard as the "kangaroo effect", it was more like a repetitive first gear jerk is probably the best way i can describe it.

[BzsBimmer]

Doesn’t sound normal. I’d pass