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      01-08-2013, 08:06 PM   #1
VictorH
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Does your DCT do this?

I've now had 3 episodes of my transmission slamming a downshift at slow speeds (I'm at 49,800 miles).
Situation: Doesn't matter if it's in S mode or D mode, slowing down for a red light, always at speeds of 30 mph or less, when the car is downshifting on its own (never on a driver initiated downshift), from 4th to 3rd or like today from 3rd to 2nd for some reason the car will slam the engagement and jolt the whole car. Since there is no throttle application it doesn't do much other than just jolt the whole car. It's a bit shocking as the downshifts are at that speed are very gentle with lots of clutch slip, but when it slams there's no warning just a jolt.

It's really infrequent, only 3 times in its life and I've owned the car from new, the last time was today and it's maybe one time per year, so obviously very, very infrequent. Anyone else have this happen? I doubt that the dealer will be able to detect anything but since I'm close to out of warranty I wonder if it's worth telling the dealer.
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      01-08-2013, 08:16 PM   #2
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Definitely advise your dealer. They will open a case and even if they do not experience it or find a fault, this case will help if by chance you have failure after warranty. Just curious, have you had any software updates? A lot of these type of issues can be software related. Also, a adaption(re-learn) of your car may help as well. Are you the only driver of the car?

Quote:
Originally Posted by VictorH View Post
I've now had 3 episodes of my transmission slamming a downshift at slow speeds (I'm at 49,800 miles).
Situation: Doesn't matter if it's in S mode or D mode, slowing down for a red light, always at speeds of 30 mph or less, when the car is downshifting on its own (never on a driver initiated downshift), from 4th to 3rd or like today from 3rd to 2nd for some reason the car will slam the engagement and jolt the whole car. Since there is no throttle application it doesn't do much other than just jolt the whole car. It's a bit shocking as the downshifts are at that speed are very gentle with lots of clutch slip, but when it slams there's no warning just a jolt.

It's really infrequent, only 3 times in its life and I've owned the car from new, the last time was today and it's maybe one time per year, so obviously very, very infrequent. Anyone else have this happen? I doubt that the dealer will be able to detect anything but since I'm close to out of warranty I wonder if it's worth telling the dealer.
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      01-08-2013, 10:11 PM   #3
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Quote:
Originally Posted by VictorH
I've now had 3 episodes of my transmission slamming a downshift at slow speeds (I'm at 49,800 miles).
Situation: Doesn't matter if it's in S mode or D mode, slowing down for a red light, always at speeds of 30 mph or less, when the car is downshifting on its own (never on a driver initiated downshift), from 4th to 3rd or like today from 3rd to 2nd for some reason the car will slam the engagement and jolt the whole car. Since there is no throttle application it doesn't do much other than just jolt the whole car. It's a bit shocking as the downshifts are at that speed are very gentle with lots of clutch slip, but when it slams there's no warning just a jolt.

It's really infrequent, only 3 times in its life and I've owned the car from new, the last time was today and it's maybe one time per year, so obviously very, very infrequent. Anyone else have this happen? I doubt that the dealer will be able to detect anything but since I'm close to out of warranty I wonder if it's worth telling the dealer.
The dealer can calibrate the clutch for you and 90% of the time it will solve your issue ..

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      01-08-2013, 10:25 PM   #4
W Cole
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I'm not sure how hard of a jolt you are experiencing but mine has always done this and I am currently running the latest firmware. I swear it was smooth for about a day after the software flash and then got bad again.

I will talk to the dealer about calibrating the clutches, I haven't heard of this before.
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      01-08-2013, 11:09 PM   #5
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Quote:
Originally Posted by W Cole View Post
I'm not sure how hard of a jolt you are experiencing but mine has always done this and I am currently running the latest firmware. I swear it was smooth for about a day after the software flash and then got bad again.

I will talk to the dealer about calibrating the clutches, I haven't heard of this before.
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      01-08-2013, 11:29 PM   #6
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To OP, you track often, so maybe something related to that? I have never experienced it, but am curious as to the cause. Good luck.
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      01-09-2013, 09:23 PM   #7
VictorH
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I'm the only driver. Have never experienced this on the track. The jolt is pretty good. Would be the equivalent of side-stepping the clutch on a manual, it's not subtle it's a pretty good "bang."

I'll set up time with dealer. It's odd (but I'm happy that it's not more frequent) that it's what, one out of 12,000 shifts. You might think it would be software related but I'm not sure (no tunes of any kind on the vehicle).
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      01-09-2013, 11:26 PM   #8
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Quote:
Originally Posted by m33 View Post
The dealer can calibrate the clutch for you and 90% of the time it will solve your issue ..
m33 do you know what this procedure is called in BMW tech speak? I asked my local dealer about having this done and they said there are "no adjustments possible within the DCT system or software". This sounds like BS to me since I know for a fact that other dual-clutch systems (GT-R, EVO, etc) allow for some fine tuning via software. Maybe I should hook up the Autologic to see if it can help?
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      01-09-2013, 11:44 PM   #9
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It is called clutch curve setting and clutch slip adaptation. I have done this myself and it will be a completely different car until it re adapts to your driving style. Autologic will do it. It is typically only recommended at the dealer if your have the dct out or replaced or do clutches. I have found this to cure many complaints from people that have bought these cars from a owner that drives much different than them. This allows the DCT to adapt to new owner.



Quote:
Originally Posted by Tuner1 View Post
m33 do you know what this procedure is called in BMW tech speak? I asked my local dealer about having this done and they said there are "no adjustments possible within the DCT system or software". This sounds like BS to me since I know for a fact that other dual-clutch systems (GT-R, EVO, etc) allow for some fine tuning via software. Maybe I should hook up the Autologic to see if it can help?
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      01-09-2013, 11:50 PM   #10
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Yeah, with it being so sporadic it does not sound software related, but I would start at the basics in any case. Your DCT brain may be optimized for the track now and that is why no issue there. These DCT's try to anticipate what you are going to do next,all the time, and it may think it is track time


Quote:
Originally Posted by VictorH View Post
I'm the only driver. Have never experienced this on the track. The jolt is pretty good. Would be the equivalent of side-stepping the clutch on a manual, it's not subtle it's a pretty good "bang."

I'll set up time with dealer. It's odd (but I'm happy that it's not more frequent) that it's what, one out of 12,000 shifts. You might think it would be software related but I'm not sure (no tunes of any kind on the vehicle).
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      01-10-2013, 12:19 AM   #11
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Quote:
Originally Posted by VCMpower View Post
It is called clutch curve setting and clutch slip adaptation. I have done this myself and it will be a completely different car until it re adapts to your driving style. Autologic will do it. It is typically only recommended at the dealer if your have the dct out or replaced or do clutches. I have found this to cure many complaints from people that have bought these cars from a owner that drives much different than them. This allows the DCT to adapt to new owner.
Thanks for the info. I will hook up the Autologic tomorrow

My DCT is behaving differently during automated, decel, off-throttle downshifts since adding the supercharger. Hopefully this can be tuned out.
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      01-10-2013, 12:44 AM   #12
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Quote:
Originally Posted by Tuner1
Quote:
Originally Posted by VCMpower View Post
It is called clutch curve setting and clutch slip adaptation. I have done this myself and it will be a completely different car until it re adapts to your driving style. Autologic will do it. It is typically only recommended at the dealer if your have the dct out or replaced or do clutches. I have found this to cure many complaints from people that have bought these cars from a owner that drives much different than them. This allows the DCT to adapt to new owner.
Thanks for the info. I will hook up the Autologic tomorrow

My DCT is behaving differently during automated, decel, off-throttle downshifts since adding the supercharger. Hopefully this can be tuned out.
I know some will disagree, but the fact remains that engine braking is changed after a SC install and that is one of the "inputs" that the dct is looking at. I also felt a change in shift characteristics after SC install.
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      01-10-2013, 09:33 AM   #13
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I believe this !
My car shifts a lot smoother then it did when I first drove the car in brand new form..

It's bugged out witnessing the calibration process of the tranny ECU being performed ...
It goes through everything ! Oil temp grip, release, hard engagement , soft engagement
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      01-10-2013, 11:40 AM   #14
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Quote:
Originally Posted by VCMpower View Post
...but the fact remains that engine braking is changed after a SC install and that is one of the "inputs" that the dct is looking at. I also felt a change in shift characteristics after SC install.
I certainly agree with you. The change in automated, low-speed downshifting is IMO due to the supercharger. It is a minor irritation relative to the joy that the extra power from the SC provides but it would be nice if the Autologic calibration can improve the situation.
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      01-10-2013, 12:30 PM   #15
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Quote:
Originally Posted by m33 View Post
I believe this !
My car shifts a lot smoother then it did when I first drove the car in brand new form..

It's bugged out witnessing the calibration process of the tranny ECU being performed ...
It goes through everything ! Oil temp grip, release, hard engagement , soft engagement
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      01-10-2013, 12:32 PM   #16
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It should improve it for you. If not, rest assured it is not a "fault" in you DCT. Good luck with this.


Quote:
Originally Posted by Tuner1 View Post
I certainly agree with you. The change in automated, low-speed downshifting is IMO due to the supercharger. It is a minor irritation relative to the joy that the extra power from the SC provides but it would be nice if the Autologic calibration can improve the situation.
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      01-11-2013, 07:29 AM   #17
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I've had mine bang a couple of times. I think maybe twice? Then it was downshifting slow in D2 when I would come to a corner, slow down and the DCT would stay in 4th.

Only issues I've had so far with the DCT. I also had a rough idle and eventually constantly would go into limp mode. About 2 weeks ago, I had a vacuum sensor near the brake booster replaced which seems to have cured everything. Hadn't had a slow downshift or a bang yet.
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      10-10-2013, 12:20 PM   #18
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Quote:
Originally Posted by VCMpower View Post
I know some will disagree, but the fact remains that engine braking is changed after a SC install and that is one of the "inputs" that the dct is looking at. I also felt a change in shift characteristics after SC install.
I've definitely experienced this. The Engine braking is what bothers me the most. It makes downshifts almost impossible to be smooth.
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