MDCT Shift Mode vs. Wear and Tear

alpinecoupe · 11-10-2008, 12:17 AM

Not fully understanding how the MDCT functions I have a few questions regarding longevity / wear and tear related to the shift mode selected.

I have owned several sports cars with manual gearboxes and learned to heal and toe / match rpms on downshifts many years ago.

In the higher, more aggressive shift modes the engine rpms are "blipped" to provide the same effect. Does this reduce wear and tear on any of the gearbox internals e.g. clutches, synchromesh (or whatever equivalent mechanism is used) as it does on a manual gearbox?

On the flip side, when driving hard the shifts in the upper modes are fairly harsh. Not that I mind it but does this cause more wear equivalent to "slamming gears" in a manual box?
I know on some older Porsches I owned you could get a feel for how fast to shift. If you pushed it faster, you would accelerate wear on the synchromesh rings.

Obviously if I'm driving the car really aggressively I would expect more wear and tear. My M3 is a daily driver and I do not "thrash" on it, but do enjoy some spirited driving when the time and place are appropriate.

Just wanted to see if anyone knows if leaving it in a specific shift mode for daily use will prolong, or shorten the life-span of the gearbox components.

Thanks.

watrob · 11-10-2008, 02:24 AM

I don't think you will own the car long enough to get a transmission problem with the DCT box. If it was weak they would not let you use LC like Nissan does with there GT-R.

Drive it how you feel it works the best for you, you bought the car to enjoy, not to pass it onto someone else in 2-3 years tim to enjoy. It will hold together plus you have a warranty.

mkoesel · 11-10-2008, 09:19 AM

The rev-matched downshifts should definitely help extend longevity. I have wondered about how the aggressive up-shifting effects them also. I think these clutches are designed to be more durable than a typical manual transmission under aggressive shifting. For one thing, they are wet clutches which should in theory reduce wear. And for another thing, there is no throwout bearing or other mechanical linkage to wear. That's just my speculation though - I don't think there are any hard numbers as far as clutch-life yet since this type of transmission is so new.

swamp2 · 11-10-2008, 12:55 PM

This is a good question.

As mkoesel stated the rev match on downshift will help smooth them and to some small extent lessen wear. This car has syncros just like a MT, on the inside it is very similar to a MT. It's not exact by any stretch, but in principle identical.

As far as the upshifts there is indeed a big difference between S3 and S5/S6 during high rpm shifts. Of course we will almost for sure never be able to prove it, but with the large jerk (surge, thump, etc. whatever you want to call it) in those modes I think it must be more taxing and wearing on the system, clutches, gears and maybe even to some small extent some bushings in the drive system. I'm sure BMW, Getrag and Borg Warner know the answer fairly precisely but they won't be saying anything either.

Dascamel · 11-10-2008, 04:18 PM

What would you guys guess, 60k, 90k, 120k+ if not overly abused and maintained?

mkoesel · 11-10-2008, 04:47 PM

Quote:

Originally Posted by Dascamel

What would you guys guess, 60k, 90k, 120k+ if not overly abused and maintained?

I sure hope its over 120k or this will be my first and last non-manual-transmission equipped car.

swamp2 · 11-10-2008, 05:59 PM

Had over 200k miles on my E36 M3 MT. It was designed for the Euro version of the car with 320 or so hp (mine had maybe 275, moded). I never had any transmission nor clutch problems and all parts were orginial. I only occasisonally went to driver events such as autoX or track days but did do a lot of hard "canyon runs". My guess is that the new unit will be good for just as many miles, maybe more. I think it is rated for use in the next M5 meaning is has some nice design margin like in the E36 case which will only help on lifetime. Obviously heavy use at the strip or track will reduce the lifetime of any transmission, MT, AT, AMT, etc.

11-10-2008, 12:17 AM	#1
alpinecoupe Enlisted Member 8 Rep 38 Posts Drives: 2008 M3 Coupe Join Date: Aug 2008 Location: Oregon / USA iTrader: (0)	MDCT Shift Mode vs. Wear and Tear Not fully understanding how the MDCT functions I have a few questions regarding longevity / wear and tear related to the shift mode selected. I have owned several sports cars with manual gearboxes and learned to heal and toe / match rpms on downshifts many years ago. In the higher, more aggressive shift modes the engine rpms are "blipped" to provide the same effect. Does this reduce wear and tear on any of the gearbox internals e.g. clutches, synchromesh (or whatever equivalent mechanism is used) as it does on a manual gearbox? On the flip side, when driving hard the shifts in the upper modes are fairly harsh. Not that I mind it but does this cause more wear equivalent to "slamming gears" in a manual box? I know on some older Porsches I owned you could get a feel for how fast to shift. If you pushed it faster, you would accelerate wear on the synchromesh rings. Obviously if I'm driving the car really aggressively I would expect more wear and tear. My M3 is a daily driver and I do not "thrash" on it, but do enjoy some spirited driving when the time and place are appropriate. Just wanted to see if anyone knows if leaving it in a specific shift mode for daily use will prolong, or shorten the life-span of the gearbox components. Thanks.
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11-10-2008, 02:24 AM	#2
watrob Lieutenant Colonel 140 Rep 1,597 Posts Drives: MY2022 X5 M-Sport 45e White Join Date: Sep 2008 Location: Brisbane - Australia iTrader: (0) Garage List 2021 Toyota Yaris Z ... [0.00] 2022 BMW X5 G05 e45 [0.00] 2015 Ferrari Cali T [0.00]	I don't think you will own the car long enough to get a transmission problem with the DCT box. If it was weak they would not let you use LC like Nissan does with there GT-R. Drive it how you feel it works the best for you, you bought the car to enjoy, not to pass it onto someone else in 2-3 years tim to enjoy. It will hold together plus you have a warranty. __________________ MY22 X5 M-Sport 45e White, 22"rims, Red Calipers, Ceramic Pads. Better off saying what it does not have and that's a B&O Audio System, otherwise all option boxes are ticked.
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11-10-2008, 09:19 AM	#3
mkoesel Moderator 7515 Rep 19,368 Posts Drives: No BMW for now Join Date: Jun 2006 Location: Canton, MI iTrader: (1)	The rev-matched downshifts should definitely help extend longevity. I have wondered about how the aggressive up-shifting effects them also. I think these clutches are designed to be more durable than a typical manual transmission under aggressive shifting. For one thing, they are wet clutches which should in theory reduce wear. And for another thing, there is no throwout bearing or other mechanical linkage to wear. That's just my speculation though - I don't think there are any hard numbers as far as clutch-life yet since this type of transmission is so new.
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11-10-2008, 12:55 PM	#4
swamp2 Lieutenant General 611 Rep 10,407 Posts Drives: E92 M3 Join Date: Sep 2006 Location: San Diego, CA USA iTrader: (3)	This is a good question. As mkoesel stated the rev match on downshift will help smooth them and to some small extent lessen wear. This car has syncros just like a MT, on the inside it is very similar to a MT. It's not exact by any stretch, but in principle identical. As far as the upshifts there is indeed a big difference between S3 and S5/S6 during high rpm shifts. Of course we will almost for sure never be able to prove it, but with the large jerk (surge, thump, etc. whatever you want to call it) in those modes I think it must be more taxing and wearing on the system, clutches, gears and maybe even to some small extent some bushings in the drive system. I'm sure BMW, Getrag and Borg Warner know the answer fairly precisely but they won't be saying anything either.
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11-10-2008, 04:18 PM	#5
Dascamel Lieutenant Colonel 48 Rep 1,664 Posts Drives: 2008 e92 M3, 2010 e91 328i Join Date: Jul 2007 Location: Bakersfield, CA iTrader: (0)	What would you guys guess, 60k, 90k, 120k+ if not overly abused and maintained? __________________ 2008 E92 M3 Jerez Black,DCT,Fox Red ext,Prem,Tech,19", ipod/usb, CF roof and trim 2010 E91 328i Space Gray,Black int, M sport, most options 2007 Montego Blue 335i (retired)
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11-10-2008, 05:59 PM	#7
swamp2 Lieutenant General 611 Rep 10,407 Posts Drives: E92 M3 Join Date: Sep 2006 Location: San Diego, CA USA iTrader: (3)	Had over 200k miles on my E36 M3 MT. It was designed for the Euro version of the car with 320 or so hp (mine had maybe 275, moded). I never had any transmission nor clutch problems and all parts were orginial. I only occasisonally went to driver events such as autoX or track days but did do a lot of hard "canyon runs". My guess is that the new unit will be good for just as many miles, maybe more. I think it is rated for use in the next M5 meaning is has some nice design margin like in the E36 case which will only help on lifetime. Obviously heavy use at the strip or track will reduce the lifetime of any transmission, MT, AT, AMT, etc.
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