DCT "thud" while stationary

[L3stat]

Hi guys, I've searched through but didn't find anything similar hence a new post. Wondering if anyone has experienced the same issue.

My 2010 E90 drives and works fine, around 50k miles now, no shifting problems. Of late, I've noticed that during longer waits at the lights (in D), there would randomly be a soft "thud", accompanied by a slight twitch that can be felt (as if someone nudged the car forward slightly). But the car does not move/creep forward. Take off after lights go green is normal after. I haven't waited long enough at any lights for this to happen twice in a row. It's hard to record because it's pretty random as well.

This feels intuitively like a DCT thing, and I haven't done anything else to the car recently that could remotely explain the sound or nudge (e.g. replaced wheel speed sensor in June but should be unrelated). This is my third M3, but I've not ever noticed this before with my first E90 and subsequent F80. Just weird. Dinan's DCT software was installed when I got it, but I flashed that out with factory software back in May. Again, should be unrelated.

The car does not throw any errors, and up on a hoist, the lower pan looks dry (previous owner had it replaced), while there's slight seepage from the side pan (was not done previously). I believe the oil levels in the DCT are fine, otherwise the car would have thrown an error? Also, shifting feels normal, no lags or other peculiarities.

Has anyone else experienced this before? Is this normal? What could be the cause? The workshop I went to didn't have a strong view on what the cause could be, but suggested that the DCT is sensitive to the fluid it runs. I have no idea what was used when the lower pan was replaced by the previous owner. They suggested a fluid flush, but I thought since the side pan was seeping, this would be a good time to get that addressed as well.

Appreciate any thoughts/guesses! Thanks!

[roastbeef]

this is normal and it happens to me from time to time, and i've seen other threads describing the same symptoms.

what i would theorize it is, is just a "hiccup" that causes the clutch to engage and then disengages once it figures out you're stopped with your foot on the brake.

[exVtekGuy]

Originally Posted by roastbeef

this is normal and it happens to me from time to time, and i've seen other threads describing the same symptoms.

what i would theorize it is, is just a "hiccup" that causes the clutch to engage and then disengages once it figures out you're stopped with your foot on the brake.

I concur. had same issue, searching the forum seemed to indicate it's seen in many cars. I did have the dct adaptation reset a while back and I haven't noticed the issue lately.

[m3peat]

Originally Posted by roastbeef

this is normal and it happens to me from time to time, and i've seen other threads describing the same symptoms.

what i would theorize it is, is just a "hiccup" that causes the clutch to engage and then disengages once it figures out you're stopped with your foot on the brake.

Same for me and I've accepted it.

[L3stat]

Hi guys, thanks for the inputs! I must have been searching for the wrong terms, most DCT threads either talk about the leaks or juddering when the car is moving. It is still strange to me that I haven't noticed this with my past 2 cars, granted maybe the F80 is not an apples-to-apples comparison. I guess in your opinion still a good idea to get that weeping side panel addressed?

[SDPLV]

Definitely normal. I will say for me it happens more when I'm stopped at a light with M button engaged. So Euro MDM, Power at sport plus, Servo at max, Shift speed at S4 or S5, and EDC in sport,

[L3stat]

Thanks guys!

[Sneaky Pete]

One thing that does cause that sort of effect is the park brake...which is a parking pawl system.
If it disengages under load you will get a thud.
Why it would be doing it in your situation is not obvious.
Are you shifting into neutral?

[L3stat]

Hi Pete, yeah I'm familiar with the parking pawl sensation when putting into D. What I experienced is nowhere as "violent", just a gentle nudge, and no the car doesn't go into N. Just to update I've since replaced all the DCT seals and have fresh oil. The car still does it sporadically. I think I'll have to learn to accept it.

[Rainer M]

Originally Posted by L3stat

Hi Pete, yeah I'm familiar with the parking pawl sensation when putting into D. What I experienced is nowhere as "violent", just a gentle nudge, and no the car doesn't go into N. Just to update I've since replaced all the DCT seals and have fresh oil. The car still does it sporadically. I think I'll have to learn to accept it.

Mine does the same thing.
It didn't get worse over the years so I just accept that's a fluke.
I drive about 30.000 miles on it and it's ok.

[dparm]

I'd say it's somewhat normal. The DCT is self-adjusting so the clutches might just be slipping a little bit differently.

Could always change the fluid out and re-run the adaptation, but generally you shouldn't need to (unlike the older SMGs).

[neilum]

MY 11 DCT does the same exact thing. It occurs randomly, and feels like an audible thud or clunk, but only at a stop when the car engages from N to D.

Strangely this first popped up after I had the DCT fluid serviced, but it could be a coincidence. Knock on wood it hasn't happened in about 2 weeks so I'm not that worried about it, and also a little relieved I am not the only one.

Otherwise the car is flawless so I am chalking it up to a minor DCT hiccup and its nothing to worry about.

[amrazM]

Are you holding the brake when at a stop?

[madrit21]

I have this same problem. I had a gts flash, reset adaptations, and a transmission fluid flush done. Still the same problem. Only seemsto happen on accelerations from a dead stop. Extremely annoying.

[aswy6]

Originally Posted by amrazM

Are you holding the brake when at a stop?

Is it not advised to hold a brake when at the traffic light?

[L3stat]

Originally Posted by amrazM

Are you holding the brake when at a stop?

Nope, in D at a stop the clutch is disengaged. If I guess correctly where you're going with this question, maybe the software thinks I wanna go, and momentarily engages the clutch causing the nudge. This did cross my mind but out of habit I usually leave my foot off the brake at a stop.

[Pro-AM3]

could be normal, could be not normal. check your driveshaft and differential bolts are all still tight and snug

[madrit21]

Originally Posted by L3stat

Hi guys, I've searched through but didn't find anything similar hence a new post. Wondering if anyone has experienced the same issue.

My 2010 E90 drives and works fine, around 50k miles now, no shifting problems. Of late, I've noticed that during longer waits at the lights (in D), there would randomly be a soft "thud", accompanied by a slight twitch that can be felt (as if someone nudged the car forward slightly). But the car does not move/creep forward. Take off after lights go green is normal after. I haven't waited long enough at any lights for this to happen twice in a row. It's hard to record because it's pretty random as well.

This feels intuitively like a DCT thing, and I haven't done anything else to the car recently that could remotely explain the sound or nudge (e.g. replaced wheel speed sensor in June but should be unrelated). This is my third M3, but I've not ever noticed this before with my first E90 and subsequent F80. Just weird. Dinan's DCT software was installed when I got it, but I flashed that out with factory software back in May. Again, should be unrelated.

The car does not throw any errors, and up on a hoist, the lower pan looks dry (previous owner had it replaced), while there's slight seepage from the side pan (was not done previously). I believe the oil levels in the DCT are fine, otherwise the car would have thrown an error? Also, shifting feels normal, no lags or other peculiarities.

Has anyone else experienced this before? Is this normal? What could be the cause? The workshop I went to didn't have a strong view on what the cause could be, but suggested that the DCT is sensitive to the fluid it runs. I have no idea what was used when the lower pan was replaced by the previous owner. They suggested a fluid flush, but I thought since the side pan was seeping, this would be a good time to get that addressed as well.

Appreciate any thoughts/guesses! Thanks!

I think im having the same issue. Heres a clip of whats going on with mine. Let me know if its similar to your problem..

[amrazM]

Originally Posted by madrit21

I think im having the same issue. Heres a clip of whats going on with mine. Let me know if its similar to your problem..

Sorry but it looks like you need a mechatronics unit, that’s def not normal.

[madrit21]

Originally Posted by amrazM

Sorry but it looks like you need a mechatronics unit, that's def not normal.

Mechatronics was tested and turned out to be good. No idea what else it could be. There is no SES lights on. Not throwing any codes.