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      10-28-2012, 08:28 AM   #1
Asbjorn
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Cool DCT noises...

Hi all,

Is it normal that the DCT starts to make tiny clicking noises just before gear shifts when warm? [edit: No, this was because my gearbox was still leaking oil, see further down] (only audible with windows up and roof closed) I had my transmission repaired due to a small leak just after taking ownership of the car at around 25.000km, and I do not remember if it was there before changing oil pan and sealing. I worry if the dealer screwed something up...

Here are the noises that I hear from my DCT in order of volume.

1) the loudest noise is the clunk when engaging or disengaging D or R from/to N or P. I believe this is 100% normal and does not concern me. [EDIT: the noise probably comes from the differential. 2nd EDIT: after having the gearbox repaired, this sound now also seems to be less present]

2) there is also sometimes a similar clunk when bringing the car to a stop while the transmission in D. I believe this is normal as well and depends on how the brake pedal is operated around the speed where the creep function is active. I found that other users in here reported the same sound. Not a concern then. [EDIT: the noise probably comes from the differential]

3) finally I get two less audible noises. A few click/tick sounds just before a new gear is engaged and a turbinish whine which is modulated by the revs and seems to peak somewhere between 3000-3500 rpm and again above 5000rpm. Both noises are not there when the engine is cold! They start only after the engine oil temperature has been warm for some time. That is why I think it is related to the temperature of the transmission oil, which may reach higher temperatures only some time later than the engine oil. But I do not know. I think it starts only after +20kms of driving, but again, I am not sure exactly when. [edit: The ticking sounds disappeared after I had the DCT repaired again. The whine is probably related to the turbos...]

I have never had any warnings of the DCT over-heating, and it has always worked brilliantly. It is smooth as silk in normal, no matter if it is hot or cold, and it is fast, solid and punchy in sports and manual modes.

Are other Getrag DCT owners (which excellent ears) experiencing these noises?

Last edited by Asbjorn; 11-29-2012 at 01:47 AM..
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      10-28-2012, 10:51 AM   #2
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Are you 100% sure that the noises you describe on 2) and 3) are not from your differential?

On leaky dct gearboxes there is a clear strategy by bmw to replace the whole unit, not just flush it.

The whining noise is what concerns me most to be honest.
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      10-28-2012, 11:51 AM   #3
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The part they replaced is displayed here

http://parts.bmwofsouthatlanta.com/p...107842385.html

code 28107842385

The noises described in 2) and 3) are very different actually. You may be right that the noises described in 1) and 2) both come from the differential and not the DCT itself! My differential does seem to have a little slack. It makes sense that it could make such a noise when changing from no load or engine braking/reverse to normal load as it does in 1) and 2). And as you said, that would not be such a big concern. Its the DCT which is expensive to replace...

The more quiet clicking and whining noises are clearly related to the DCT preparing to change gears and the revs. And at the same time they are related to temperature as explained...

You do not get any of these noises at all?
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      10-29-2012, 04:55 AM   #4
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Definitely not the turbining whining noise you describe.
I posted a while back a thread regarding dct lube flushing, search it as I can't redirect you at the moment along with a bmw tis document regarding occasions of leaky dct gearboxes (try googling for this, I don't think you will find it on the forum).
Does your gearbox still leak, have you checked it again?
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      10-30-2012, 02:14 PM   #5
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I had my dct replaced due to vibration. The replacement is superb but I too get a whine when fully warmed up but only at WOT/full power and certain revs. I'm not concerned, it's 300+ BHP hurling the car forward, I'd be worried if it was quiet!
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      10-30-2012, 11:44 PM   #6
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Quote:
Originally Posted by ManiacGT View Post
I had my dct replaced due to vibration. The replacement is superb but I too get a whine when fully warmed up but only at WOT/full power and certain revs. I'm not concerned, it's 300+ BHP hurling the car forward, I'd be worried if it was quiet!
Thanks alot for letting us know ManiacGT! It sounds like we have the same noise, whether its coming from that DCT or not...

And good idea Jannisa, I will have BMW check my DCT for any new leaks asap. Just to make sure. I also did a search as you recommended. I can see I am not the only one who had that plastic part replaced among the getrag DCT owners. It seems that in the beginning they would replace the whole DCT, but now they just repair it when/if leaks occur.

So no small, near inaudible, clicks just before each gear change anyone? Again only when the car is fully warmed up?
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      10-31-2012, 10:47 AM   #7
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No sounds from my gearbox when shifting, just the thunk into D1 when coming to a stop.
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      11-04-2012, 08:45 PM   #8
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A short update
The turbinish whine must have been the turbos running higher boost and getting hot due to spirited driving. It seems the noise is less when lowering the boost by switching from ESS stage 2 (390bhp) to stage 1 (350bhp).
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      11-05-2012, 04:18 AM   #9
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Great news.
To be honest I prefer stg1, I feel it's more refined and throttle response is more linear (or I 'm just getting older )
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      11-20-2012, 06:08 AM   #10
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Quote:
Originally Posted by jannisa View Post
Does your gearbox still leak, have you checked it again?
Finally had it checked for the first time since they replaced that DCT plastic part back in April this year. And yup, it still leaks. This was really a great tip Jannisa, thanks alot!

Tomorrow the fun begins as I show for my scheduled appointment at the repair shop. I am out of warranty, and I wonder how far the official BMW receipt from April will get me. I only know for sure that the price of a new DCT gearbox is around 20.000 USD here in China.
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      11-20-2012, 12:51 PM   #11
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Quote:
Originally Posted by Asbjørn View Post
. I only know for sure that the price of a new DCT gearbox is around 20.000 USD here in China.
hope it doesn't come to a full replacement. good luck
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      11-20-2012, 11:15 PM   #12
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Latest update. Attached are some pictures.

They now claim that the leak is coming from the side cover. Whether or not the bottom oil pan should have been replaced back in April remains unknown.

I want them to admit that the first repair did not fix the problem. A new leak should not occur so soon after the first repair. I also want to see if I can buy extended warranty or insurance after the repair.

Here is the full story.

In late march BMW chengdu checked the car, no oil leak problems found. (maybe at 25.000km)

In late april BMW tianjin (another dealer) identified that the transmission leaked oil. They randomly found it because I went there to buy a new battery for the car. They said it was a minor issue and normal for 3 year old cars...
BMW tianjin repaired the transmission shortly after at my expense. They replaced the bottom oil pan. (maybe at 30.000km)

Later I took the car in for engine oil change and other minor regular services at different BMW tianjin shops during the summer. No problems mentioned...

Now I asked another BMW dealer to check specifically if the transmission leak was fixed properly. (Because of this forum). They found that it was not fixed, and that a different part should be replaced. (now 39.000km)
Attached Images
    
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      11-29-2012, 01:41 AM   #13
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Smile

Wow, my gearbox is much more quiet now!

My local BMW dealer just finished replacing the gasket of the mechatronics unit and a cable harness which was also leaking oil... They also flushed the gearbox with Pentosin BMW-DCTF-1, SAE 75W.

The small ticking sounds that I used to have before each gear change when fully warm are now completely gone.

Again a big thanks to Jannisa for recommending having BMW check the car for new leaks!

Last edited by Asbjorn; 11-29-2012 at 01:50 AM..
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      11-29-2012, 03:18 AM   #14
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Thank you for your kind words but it was nothing you should thank about, it was just a matter of time until you had the mechanics visually check the gearbox.

Thank God it is now fixed at no cost for you and all your worries disappeared.

If I were you I would beat the shyt out of it repeatedly just to make sure no air bubble is trapped because of the flush.

Enjoy it, I know you will
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      11-29-2012, 09:54 AM   #15
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Yep, glad you got it sorted... do you still get the whine that you mentioned? I've not heard it in mine since so I've no idea why it did it previously.
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      11-29-2012, 10:07 AM   #16
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Quote:
Originally Posted by jannisa View Post
Thank God it is now fixed at no cost for you and all your worries disappeared.
Yup, except I am out of warranty here in China, so it did cost me! But not as much as a new DCT-box would have!
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      11-29-2012, 10:27 AM   #17
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Quote:
Originally Posted by ManiacGT View Post
Yep, glad you got it sorted... do you still get the whine that you mentioned? I've not heard it in mine since so I've no idea why it did it previously.
Yes!

I am now back to the OEM tune, and there is still a whine, but again only when the car is warm. The pattern is different from before, but whether it is related to ESS, the DCT or something completely else I do not know yet. This near inaudible whine now peaks at around 1600 rpm, but disappears at higher and lower revs.

I have studied videos of "tired" N54 turbos such as this



But even the sound of my "whine" is similar, I have found it is strictly related to rpm, and not related to load like yours. Mine is present even in N if I go to 1600rpm. Actually it does not get any louder while accelerating.

And since the turbo rpm does not follow engine rpm, it might be something else...

hm hm hm
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      11-30-2012, 07:21 AM   #18
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Parts of the DCT still turn in N so could still be that... more likely engine tho, belts perhaps? Try some belt dressing spray on the belts and see if that helps. I had this with my old e85 and the belt dressing was great in getting them to go quiet.
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