M4 Slams in Gear ...normal?

[Racing Instructor]

At the track (Sebring) with the setting as in the picture, the car really slams into gear. Even when doing 110mph and automatic shift the rear wheels chirp. Is this normal? Have you guys have experienced this too? Is it bad for the car? Is it normal?

Running MPSS and stage one Dinan. GTS gearbox coding.

Thanks for your help

[allinon72]

It's not all that uncommon with the Drivelogic at 3 and MPSS.

[mcvaughan]

I think that's what makes the DCT transmission so compelling on the track — the lightning fast shifts. I believe BMW made this gearbox fairy robust, compared to the predecessor, SMG.

[MRV99]

So what your really asking is does other people's tires chirp on shifts and not "transmission slam" which in my eyes would mean a bang or abrupt noise from the transmission when shifting.

These cars have high horsepower/high torque and any reduction then adding of power/torque can chirp the tires. I assume you are feeling the tires chirp, the nanny's kick in reducing power and then power back on. With a not so sticky tire like the MPSS, I am assuming this is what your experiencing.

[Racing Instructor]

Originally Posted by MRV99

So what your really asking is does other people's tires chirp on shifts and not "transmission slam" which in my eyes would mean a bang or abrupt noise from the transmission when shifting.

These cars have high horsepower/high torque and any reduction then adding of power/torque can chirp the tires. I assume you are feeling the tires chirp, the nanny's kick in reducing power and then power back on. With a not so sticky tire like the MPSS, I am assuming this is what your experiencing.

Yes, it is the slam but the traction control is set to OFF, not MDM OFF, but as far as I know the TC is off. I don't like that transmission slam because it upsets the car and while it is not too big of a thing on the straights, it becomes a real issue when the transmission slams in a curve.

I tried shifting manually but doesn't help either, lifting when shifting make the car unstable.

[CanAutM3]

Originally Posted by Racing Instructor

Yes, it is the slam but the traction control is set to OFF, not MDM OFF, but as far as I know the TC is off. I don't like that transmission slam because it upsets the car and while it is not too big of a thing on the straights, it becomes a real issue when the transmission slams in a curve.

I tried shifting manually but doesn't help either, lifting when shifting make the car unstable.

In my experience, the DCT will do a powershift when upshifting in a straight line in the more aggressive settings to recuperate the engine inertia for optimal acceleration. However, the DCT is quite smart and will execute a butter smooth shift if it senses lateral acceleration as to not upset the chassis balance. This is actually a benefit of DCT, where one can shift mid corner without unsettling the car. I would definitely recommend using sequential modes (manual) on the track so you, as the driver, selects when the shifts occur.

Odd questions coming from a "racing instructor" though...

[nicknaz]

You can also use "S2" setting for a less aggressive gear change, even in the straights. (That's what I personally prefer in the rain)

[Racing Instructor]

Originally Posted by CanAutM3

Odd questions coming from a "racing instructor" though...

Not really odd...slamming gear change upsets the car and it seems to me that that is not right. Turns out it was not right and BMW replaced the gearbox.

Odd that you found this an odd question....

[FLOSS M]

I have used S3 with sport plus all 3 settings on the track. On R888R's (305/35/18) it will trip the traction light on shifts. S2 decreases the frequency of that happening.

[darkbluemn]

Well, not sure if the slam u mean the kicking back when upshift, kind of over rev and release clutch suddenly.

If that's the case, it's normal and it's how u gain performance. Ur gearbox will shift smoothly when it senses lateral G force. A good example for me is shifting to 5th gear after uphill esses at Watkins Glen, flat out at 125+ in corner and shift, super smooth, but a little slower shifting.