gearbox knock when starting engine from stop-start

[carl0s]

Hi. Is this normal? When the engine starts itself from stop/start, there's a knock as though the gearbox is knocking against the transmission tunnel.

I tried to record it here:

[carl0s]

I've read elsewhere that this could be the gearbox putting itself into Park when stopped. Hmm. It would make sense I suppose. Does anyone know if that's true? Park is usually a solenoid into the output shaft isn't it.

The car had stop/start coded to 'always off by default' when I got it, and I have coded it back to normal.

[Havy]

Hello

I had the same problem!

Had the car checked by several BMW partners and finally got the correct answer from BMW Frankfurt!
None of the 3 BMW Partners could give the correct explanation.

According to the gear box specialist of BMW Frankfurt it is normal. The noise is actually caused by the hydraulic pressure valve. Thus preventing the gear box switching in to P as it would normally do when the car is switched off.
This noise is typical to M cars having this type DCT.

Cheers

[carl0s]

Originally Posted by Havy

Hello

I had the same problem!

Had the car checked by several BMW partners and finally got the correct answer from BMW Frankfurt!
None of the 3 BMW Partners could give the correct explanation.

According to the gear box specialist of BMW Frankfurt it is normal. The noise is actually caused by the hydraulic pressure valve. Thus preventing the gear box switching in to P as it would normally do when the car is switched off.
This noise is typical to M cars having this type DCT.

Cheers

Hi, thanks Havy! It's good to know it's normal.
Thanks for confirming.
I must say, it's pretty terrible NVH for a premium luxury car. I'm surprised BMW thought this was OK, and didn't do something to quieten it down.
I wonder if the solenoid or valve has an adaptation procedure that can be run, like what is usually done for gearbox valve bodies.

Here's another video I made at a moment's notice today:

[Havy]

Year, I was also very I called even the tech in Munich and complained about the noise. A luxury car 150k+ with a noise when it’s off at a traffic light.
The tech in Frankfurt explained the function in detail and said that you have to take that pill as it is a manual gear box wich gears automatically. If you had the “P” position there would not be such noise. Either you have that damn good gear box or not.
Since I know that I switch off the auto start stop.

[Whipple]

I’m curious now, I never used the on/off feature, I will see if this noise happens,if there saying it’s normal it should.

[carl0s]

I think I'd sooner have no clunk and a ZF 8HP. The ZF is smoother, changes quickly enough (easily), and is more eager to change gear in relation to throttle pedal input. A much more fluid box in both take-off (torque converter) and general driving.

[Taheemr]

I can assure this is normal, my old m6 did it, as does my new one, my mates f10 also does it. Also see if you also get a thud when engaging reverse of 1st from an overnight cold start, i get this and it can be quite harsh


let me know

Thanks

by the way I am with you on the auto, other will disagree

[UnfoundLegend]

The sound you are hearing is normal but fixable. You also may hear it when first starting the car and shifting to N, D, or R.

Using ISTA-D, you must run a few ABL service functions (gearbox adaptation procedure, reset all adaptations [including incremental wheel]). This will make the gearbox relearn itself and will feel very solid and crispy.

The dealership should be able to do this for you. If out of warranty, it's very simple to do yourself.

[Taheemr]

Originally Posted by UnfoundLegend

The sound you are hearing is normal but fixable. You also may hear it when first starting the car and shifting to N, D, or R.

Using ISTA-D, you must run a few ABL service functions (gearbox adaptation procedure, reset all adaptations [including incremental wheel]). This will make the gearbox relearn itself and will feel very solid and crispy.

The dealership should be able to do this for you. If out of warranty, it's very simple to do yourself.

so whats the self fix

[UnfoundLegend]

Originally Posted by Taheemr

so whats the self fix

To use ISTA/D yourself:

https://www.bimmerfest.com/forums/sh.../topics/936877

[Taheemr]

Too difficult for me, I leave it to BMW

[carl0s]

Thanks. I will give this ago. I hoped there would be an adaptation procedure. I am going to program all the ECUs with latest integration level that I have this weekend. Then I'll re-code the turn signals in hud etc, and then check out the gearbox adaptations!