Gear hesitation almost got me in a bad accident

nusevad · 11-28-2008, 02:01 PM

i noticed the hesitation today, it sucks...

waremark · 11-28-2008, 08:01 PM

I have 10,000 miles on my pre-update DCT - update to 31.2 booked for Monday. Overall the DCT is an amazing transmission, and better for the car in my personal opinion either than a 6MT (I have driven one) or than a conventional auto would be.

My car has never had a delay on manual shifts, and has never stalled, so these problems with the original software do not seem to have affected all cars. I did experience the refusal to change down under threshold braking on track.

I drive the car fairly equally in D2 and in S1. I do not use higher S numbers because there is no acceleration advantage (proven in acceleration tests) and the upchanges are smoothest in S1.

In city driving, my DCT is sometimes 'clonky' on changing into 2nd gear. I am guessing that BMW have introduced the delay on changes into 2nd gear to make the transmission smoother in city driving. Perhaps I will be disappointed when I get the upgrade.

If you have a manual transmission, and you want to change from 7th (or even 6th) to 2nd, you will have a delay while you make the change. Why is it a problem for there to be a delay while the DCT makes this change? Surely you can feel that 2nd gear has not engaged yet, and wait for it to engage before you try to accelerate. Owners of a car like this should know that the DCT is not a normal auto transmission, but a computer operated manual.

My attitude to BMW quality is quite different to most of you. In buying a DCT in its first few months, I fully expected there to be some problems with it - this is a new and complex technology. SMG was improved over several years. I was just hoping that initial problems with DCT could be dealt with through software updates, and that seems to be the case, so I am quite happy.

newtom3 · 11-28-2008, 10:22 PM

btw, I also noticed this in my LR3 with drive-by-wire auto tranny... you can floor the accelerator all you want after a hard braking from high gears, and it will take a full second at least to start revving up the engine/engaging the tranny. Worse still every now and then the clutch when it finally engages does so with a huge jerk and snapping sound... it's very disconcerting.

My point is that these trannies that are driven by firmware/controller which takes in many variables, e.g. accelerator position, speed, last gear changes, etc..., seem to have problems exactly in the same scenario. Strange coincidence or a basic limitation in the design or what?

11-28-2008, 02:01 PM	#45
nusevad O! So Sour!! 552 Rep 15,615 Posts Drives: Fast 240z / Slow M3 Join Date: Apr 2007 Location: 'Merica! iTrader: (24) Garage List 1971 Datsun 240z [0.00] 2008 M3 [9.60]	i noticed the hesitation today, it sucks... __________________
	Appreciate 0 Quote

11-28-2008, 08:01 PM	#46
waremark Private First Class 2 Rep 183 Posts Drives: 08 M3 Coupe DCT Join Date: Nov 2008 Location: UK iTrader: (0)	I have 10,000 miles on my pre-update DCT - update to 31.2 booked for Monday. Overall the DCT is an amazing transmission, and better for the car in my personal opinion either than a 6MT (I have driven one) or than a conventional auto would be. My car has never had a delay on manual shifts, and has never stalled, so these problems with the original software do not seem to have affected all cars. I did experience the refusal to change down under threshold braking on track. I drive the car fairly equally in D2 and in S1. I do not use higher S numbers because there is no acceleration advantage (proven in acceleration tests) and the upchanges are smoothest in S1. In city driving, my DCT is sometimes 'clonky' on changing into 2nd gear. I am guessing that BMW have introduced the delay on changes into 2nd gear to make the transmission smoother in city driving. Perhaps I will be disappointed when I get the upgrade. If you have a manual transmission, and you want to change from 7th (or even 6th) to 2nd, you will have a delay while you make the change. Why is it a problem for there to be a delay while the DCT makes this change? Surely you can feel that 2nd gear has not engaged yet, and wait for it to engage before you try to accelerate. Owners of a car like this should know that the DCT is not a normal auto transmission, but a computer operated manual. My attitude to BMW quality is quite different to most of you. In buying a DCT in its first few months, I fully expected there to be some problems with it - this is a new and complex technology. SMG was improved over several years. I was just hoping that initial problems with DCT could be dealt with through software updates, and that seems to be the case, so I am quite happy. Last edited by waremark; 11-29-2008 at 12:33 PM..
	Appreciate 0 Quote

11-28-2008, 10:22 PM	#47
newtom3 First Lieutenant 15 Rep 361 Posts Drives: 2009 BMW M3 Coupe Join Date: Sep 2008 Location: San Jose, CA iTrader: (0)	btw, I also noticed this in my LR3 with drive-by-wire auto tranny... you can floor the accelerator all you want after a hard braking from high gears, and it will take a full second at least to start revving up the engine/engaging the tranny. Worse still every now and then the clutch when it finally engages does so with a huge jerk and snapping sound... it's very disconcerting. My point is that these trannies that are driven by firmware/controller which takes in many variables, e.g. accelerator position, speed, last gear changes, etc..., seem to have problems exactly in the same scenario. Strange coincidence or a basic limitation in the design or what?
	Appreciate 0 Quote