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      03-13-2019, 04:40 AM   #1
rsmallwo
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Unhappy DCT Overheat & Hesitation Issue - 35i

Hi All,

I've had a look round the search function and not seen much concerning my issues.

For the past several months I've noticed the DCT hesitates when selecting 1st or 2nd gear when it's rolling to a stop (under slight braking) when you go to accelerate you notice a long lag before the clutch even attempts to engage. It doesn't seem like clutch slip as it handles hill situations quite well and it doesn't feel like it's even attempting to slip the clutch abit. This issue can result in unpleasant driving characteristics, even my girlfriend comments the car feels heavy from standstill and then jerky when it engages the clutch.

I have looked for this issue across google and there are alot of complaints about the DCT in general being hesitant. But I've had the car 3 years and it didn't do this back then, it just had that "normal" auto tranny uncertainty in these typical scenarios.

My other issue which might be connected is that in the past few months when oil temp is all warmed up when conducting kickdown overtake's the amber DCT overheat warning light has come on and cut power. I wasn't driving the car particular hard. Leaving the car a few hours and all was fine again. This only occurred the once.
On a track day last week the DCT overheat warning essentially came on after several laps and then refused to go despite letting the car completely cool down to cold, it cut the power by 20/30% and kind of ruined the track day for me.

What are people thoughts and questions? The car is a 35i, 2009 build with 90k miles

Thanks,
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      03-17-2019, 08:16 AM   #2
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Have you serviced your DCT?

I have 2009 35i aswell. Started noticing some slippage on Sport+ hard shifts and gearbox had some problems in automatic mode. It hold on to gears longer and wasnt so smooth around town. This happened around 60k miles.

Had an oil and filters service done. My DCT had leaked a bit at some point from the pan gasket aswell. New gasket ,that comes with the oil change anyway, fixed that aswell. Service cost me around 500eur.

Results: No slippage in sport+ shifts, picks up quicker in low revs, automatic mode as smooth as on the day i got the car.

My car runs Cobb Stage 1 map so that may cause more slippage from the DCT when pushing the car.

On the topic of overheating: have not experienced that but here are my thoughts: M DCT is a wet clutch transmission. It means that the clutch is cooled by the oil and same oil provides lubrication to the gears etc. DCT oil is a rather special mixture between manual transimssion fluid and automatic transmission fluid because it does both jobs. In time its frictional and cooling properties or viscosity slowly change and you start to see problems.

Hope this helps.

Last edited by KennyP; 03-17-2019 at 08:45 AM..
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      03-20-2019, 06:16 AM   #3
rsmallwo
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It has been remapped and it's had the gasket pan seal/filter replaced twice now!!

I was making this post to get feedback on other that had both hesitation and and gearbox temp issues or just the gearbox temp issues.

Quote:
Originally Posted by KennyP View Post
Have you serviced your DCT?

I have 2009 35i aswell. Started noticing some slippage on Sport+ hard shifts and gearbox had some problems in automatic mode. It hold on to gears longer and wasnt so smooth around town. This happened around 60k miles.

Had an oil and filters service done. My DCT had leaked a bit at some point from the pan gasket aswell. New gasket ,that comes with the oil change anyway, fixed that aswell. Service cost me around 500eur.

Results: No slippage in sport+ shifts, picks up quicker in low revs, automatic mode as smooth as on the day i got the car.

My car runs Cobb Stage 1 map so that may cause more slippage from the DCT when pushing the car.

On the topic of overheating: have not experienced that but here are my thoughts: M DCT is a wet clutch transmission. It means that the clutch is cooled by the oil and same oil provides lubrication to the gears etc. DCT oil is a rather special mixture between manual transimssion fluid and automatic transmission fluid because it does both jobs. In time its frictional and cooling properties or viscosity slowly change and you start to see problems.

Hope this helps.
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      03-20-2019, 11:48 AM   #4
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Quote:
Originally Posted by rsmallwo View Post
It has been remapped and it's had the gasket pan seal/filter replaced twice now!!

I was making this post to get feedback on other that had both hesitation and and gearbox temp issues or just the gearbox temp issues.
Ok.

You can try looking into reseting adaptations for the dct It learns drivers behaviors etc and may start to act sluggish ,change gears slowly and so on.
I have done adaptations reset with cobb as it has a setting for clearing learnings. It did actually bring sharpness back to the shifts and throttle response. It probably cant solve overheating issues but it may solve the hesitations. There are a few tools that can do that reset. BTtool for example is one that people write about.

https://e89.zpost.com/forums/showthread.php?t=491028

Google search has more results on that matter,
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      03-26-2019, 06:40 AM   #5
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Hi Kenny,

I've had the adaptations reset by my independent garage, didn't seem to help at all.

Its at the garage tomorrow so will see what they say about it.

Thanks for your input.

Quote:
Originally Posted by KennyP View Post
Ok.

You can try looking into reseting adaptations for the dct It learns drivers behaviors etc and may start to act sluggish ,change gears slowly and so on.
I have done adaptations reset with cobb as it has a setting for clearing learnings. It did actually bring sharpness back to the shifts and throttle response. It probably cant solve overheating issues but it may solve the hesitations. There are a few tools that can do that reset. BTtool for example is one that people write about.

https://e89.zpost.com/forums/showthread.php?t=491028

Google search has more results on that matter,
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      03-26-2019, 11:36 AM   #6
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subscribed!

interested to know the problem as well. on a side note, my friend had this kind of problem last year, but once he flushed the tranny fluid, all the problems are gone.

hope your problem sorted out anytime soon mate.
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      03-28-2019, 09:43 AM   #7
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So what I have read is that the dct oil is good up to a certain temperature. If it overheats, it starts to loose its original properties. You want to avoid that. When you serviced your DCT did they add new oil, and how much, or did they reuse the old oil?

I have posted several transmission temperature logs over at spool street. My build thread is also over there. I use MHD and my logs are here

www.datazap.me/u/asbjoern

But to summarize, the DCT might go to 100C during normal street driving (with DCT cooler off), but never exceeds 90C on track (with DCT cooler on) (EDIT: correction, it does go above 90 and even 100C on track if the weather is hot enough)

I run an SSP DCT oil cooler that I can turn on and off within the cabin. This because I go on track all the time for time attack and practice. So far I have not had issues with the DCT at all. And mind you that I have killed turbos twice due to my application. I am at 120,000kms, and have already replaced the DCT oil with new oil twice during its lifetime.

Unfortunately the Z4 does not have an DCT oil cooler from factory like the M3 did, so if you want to get into serious track driving, you might want to look into aftermarket DCT coolers. In fact even M3 owners do this, and know that the only cooler that was upgraded between the M4 and M4 gt4 was the DCT cooler (taken from the M6 on the GT4).

Last edited by Asbjorn; 09-26-2019 at 01:52 AM..
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      08-06-2019, 01:40 PM   #8
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Reviving this old post - was anything ever determined to be the cause? I have a 2010 with DCT and my transmission is also exhibiting this behavior with some error codes. I usually do my own work but I took this to an Indy as I could not determine root cause. They are telling me it needs a new gear selector switch (basically the part under the shift knob). I have also seen some battery issues and read on the M3 boards that the GSS fault could cause a battery draw on the E90 M3 (which looks like it has the identical DCT).
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      10-27-2019, 05:35 AM   #9
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Unhappy

Hi All,

The issue i experience is apparent from cold, it's not heat related. I'd suggest that when upto temperature the issue is slightly less annoying but still very much there.

I don't get any fault codes, RBozzell what fault codes do you get?

I took it to another mechanic and he drove the car for several days and couldn't replicate the issue, very frustrating!!

My own suspicions are something wrong with the DCT or its VANOS related. I've had the VANOS solenoids cleaned and swapped round but no joy.

I've been progressing this issue on another forum: https://www.e90post.com/forums/showthread.php?t=1593139
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