1-2 Shift in DCT

[Charleston335]

I have a 2012 M sport 135i and I just got last week and I just noticed sometimes when im WOT and I shift anywhere from 3k-5k rpms there is a lag and jolt...Dont experience this with the other gears, anyone had this issue?

[Pangloss]

Generally speaking, the shift should be lag-free and smooth as glass. There's a lot of talk around the board about *throttle* lag, but I don't think I've heard of anyone experiencing a delay between the pulling of the paddle and the shifting of gears. And the transition itself should be very smooth (though it won't be as smooth as an automatic shift if you're flooring it, I've noticed).

Do you have the Sport button on? I don't think I've ever done manual mode without the sport button, but in theory (according to the manual) it should shift more slowly than when the sport button is off.

[Charleston335]

Yea the sport button is on, its weird like at 4K rpms when i shift into 2nd the car pauses then jerks and al lthe other shifts are fast and nice.

[ParkNuts]

Haven't had this but I do get a lag on the 4-5 shift on rare occasion. Seems like the A/C makes it worse. It's not too bad and I can't really duplicate it on demand. All other shifts are very smooth. Throttle response can be finnicky on slow roll in 1st or second but it's not from a shift at all.

[cooler2442]

Sometimes I get a bit of a jolt with an upshift or on a down shift if the car automatically down shifts. Seems like the DCT is trying to catch the gear and semi fails but still gets it. Bothers me a bit but it only happens once every 1-4 months.

[CrustyNoodle]

No lag between flipping a paddle and next gear engagement. I always drive in manual mode but not in "S" as I find the throttle response a bit too sharp. It also makes much better pops and farts in non-S mode

Cooler2442, I just read through all your mods in your sig. Don't want to thread hijack but that must be a very interesting vehicle you have there. Have you had it on the dyno?

[bogart]

OP - can you take a video of this and post it?

[Gnip Gnop]

I guess I'm lucky. I keep rfeading negative things about the DCT. Mine has no lag, and shifts so hard that if traction control is off I spin the tires when I shift to second.

[EmUc]

I notice a bit of a lag during the first manual shift going from S mode to M mode. The shift takes slightly longer than normal. Understandable due to the mode changing. No shift lag after that.

[New21er]

I can't figure out to "dyno" a DCT trans. Maybe Mr. cooler2442 can help.

[CrustyNoodle]

I think you need to press the accelerator all the way to the kick down switch without actually engaging it (in manual mode of course).

[DWRAT]

My DCT was funny acting until I hit 1200-1500 miles.
My gues is it's a break-in protection function.
After 1500 miles the car is an animal off the line, in fact to much power so I can only give it 1/2 gas on take off.

[tkruger206]

Yeah sorry to hear some of the DCT owners are having trouble with or not happy with the DCT.

I only ended up going with the DCT because I could not find a manual around Seattle when I was buying. I almost went with a manual 335i sedan but saw the used LMB 135i DCT with 9k on the clock. I figured it wouldn't hurt to have an automatic mode for traffic or when driving to work in the morning plus the hi-tech cool factor of the new DCT (it's pretty sweet how it works and I love explaining it to my car friends).

I bought my car while I was overseas and didn't drive it until I picked it up. I am not disappointed with the DCT at all, mine works flawless. Smooth in automatic mode, nice to drive in manual mode without sport on...and it shifts instantly and like a hammer when you have it in sport while kicking it in the berrys.

I find that I need to shift it more like I would on a motorcycle. You've got 7 gears and all that torque, so you don't really need to downshift much, but there is a bit of a power-band like on a bike. So if i'm passing someone on the freeway I can do it in 7th, 6th 5th, 4th or even 3rd, just depends on how quickly I want to pass and how many revs I want to have left after I get around them. All DCTs share many design similarities with motorcycle transmissions like wet clutches (I know some bikes \have dry but most bikes are wet).


In terms of how quickly it moves up and down the gears and if there is lag or delay...here is my take and how mine performs. Going up through the gears, your next gear is always engaged, so upshifts should be fast and either smooth or instant depending on if the Sport button is on and how much throttle you're giving it. If you're in manual and giving it more than half throttle, the car sounds like an F1 car shifting, there is just a POP! and instantly a lover rev sound.

When you down shift the car has to swap to the lower gear because it had the next highest one ready. So if you're in 4th and going to 3rd you have to wait an extra like 200-400 milliseconds for it to change from 5th to 3rd on the primary gear set. I still find it does this quicker and smoother than I could do on a manual, plus it makes a perfect rev-match which sounds great as you pass someone or come to a light.

In auto mode the car will hang in 7th or 6th until you drop down to about 30 MPH then it falls down to 4th or 3rd and on down to 2nd and 1st as you come to a stop. If you're in manual you can step down through each gear or double/tripple click down a couple gears and the car will do a nice rev match and drop right in, even if i'm rolling up to a light and want to hit 1st on my own to get the rev sound.

...would I rather have a manual...i dunno... I would have gone manual if I could have found one...but would I change now? I don't think so. It wouldn't be as nice in traffic or the city and man does the car make some great sounds with the DCT. So I think the DCT it equal in it's own way.


My wife picked up a MkVI GTI 2.0 Turbo with a 6 speed DCT (they call it DSG) and I think it's smoother than the Bimmer's DCT but does not have the punch/hammer quick effect when you're on it. Still shifts fast and without loss of power just feels more average vs. the Bimmer which feels race level. The Bimmer DCT is made by Getrag and the VW's is made by BorgWarner and BW has more experience with DCT so go figure. I digress though as the GTI cost half what the Bimmer did.

I also want to add that i feel the DCT solves the jerky clunky feel of the old SMG boxes, the DCT is I think smoother than even a standard auto at slow speeds.


I would encourage anyone having a poor experience to have BMW reflash the transmission module and reset it's adaptive settings.



TK

[bogart]

Video would help...

[Gnip Gnop]

I have had this happen now too.....turn DTC on or go timyoyo mode. I think it may be traction control kicking in....I don't see the light though. Once I go DTC, it does not cut power and I get a chirp from my tires which makes me think its traction control cutting power.

[Charleston335]

Hmm good observation, weird bc mine happens around 3-4K rpms but i havent drievn it in a month so havent tried it without full traction off. It didnt do it last few days i drove it either but i did get a CEL before i left to Italy.

[gman36]

turn off traction control... the dct chirps into second

[abirmaher]

With the sport button on it tends to Jolt like that. The harder you push the more you feel it, it shifts real quick but it jolts.

[BEAR-AvHistory]

Originally Posted by New21er

I can't figure out to "dyno" a DCT trans. Maybe Mr. cooler2442 can help.

Block the kick down switch. manual mode/sport button pushed. traction control off. make the run in 4th gear.

[Mr Marcus]

Originally Posted by Pangloss

Generally speaking, the shift should be lag-free and smooth as glass. There's a lot of talk around the board about *throttle* lag, but I don't think I've heard of anyone experiencing a delay between the pulling of the paddle and the shifting of gears. And the transition itself should be very smooth (though it won't be as smooth as an automatic shift if you're flooring it, I've noticed).

Do you have the Sport button on? I don't think I've ever done manual mode without the sport button, but in theory (according to the manual) it should shift more slowly than when the sport button is off.

The sport button has nothing to do with gear changes, despite being located next to the DCT unit. It controls the optimisation of engine power.

That said I agree with a few points, DSC is a pain in the ass, car feels more planted and responsive if you change to DTC. The thunk you're feeling might be DSC being too aggressive, to me it feels like hitting a pothole. I had my DCT re-flashed to solve the problem.

[Smithy7876]

From what I understand it is quite common to have a small jolt between first and second on most DTC boxes. I had the same on my last VW golf and that was a 1.6 diesel so not a power issue!

I believe it is due to having the biggest rev difference between gears. Probably needs a bit of rev matching technology to counteract it entirelly

[Jewbacca]

My experience has been that it doesn't do this in DTC or timyoyo. Also, there is a definite difference in gear change speed with the sport mode on...I don't think it's my imagination.