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      01-08-2013, 10:45 AM   #1
Munit
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Do's and Dont's for preserving DCT life

So I wanted to speak more about DCT with non-supercharged cars as that has been addressed but has sparked some interest in terms of behaviors tha may wear our DCT trannies out prematurely, especially for anyone planning on keeping the car out of warranty or long-term.

From what I gather reading there are a few things but I am not sure if they matter if you are not supercharged and on stock power/bolt on power.

1-In D mode, using D to kick down several gears slips the clutch in a way that creates a lot of heat for supercharged cars with power but is this something prematurely wearing out our cars when done often?

2-Punching it from a dead stop without launch control is not good

3-not letting the car/tranny warm up obviously

The one I was curious about is what about simply downshifting and letting the car rev match and downshift to the lower gear before you accelerate again? ie. Driving at 75 on the freeway, click the paddle down to 3rd and have foot off the accelerator during the process to let it totally engage the gear and than plant your foot? I find if you keep the accelerator pressed during a downshift it does not give you that "punch" forward in acceleration. But is it inherently bad or is it better to drop it into gear off the accelerator?
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      01-08-2013, 11:18 AM   #2
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I wouldn't keep a DCT out of warranty
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      01-08-2013, 11:42 AM   #3
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Quote:
Originally Posted by Vic311 View Post
I wouldn't keep a DCT out of warranty
Care to elaborate? Thus far the BMW DCT has proven to be a very robust unit.
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      01-08-2013, 11:55 AM   #4
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Quote:
Originally Posted by Tuner1 View Post
Care to elaborate? Thus far the BMW DCT has proven to be a very robust unit.
No I don't care to. I am not going to discuss how robust of a unit the DCT is because that would be just pure speculation (by anyone)

I am simply stating that if I owned a DCT, I would make sure I maintained a warranty because repair costs can be significant.
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      01-08-2013, 11:56 AM   #5
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      01-08-2013, 12:11 PM   #6
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Common DCT failure rate is extremely low since its first debut on the M3. There is not enough data to gather.

By the way, the cost of repairing DCT has gone down significantly over the years due to the fact that more models are using it now. Eventually, maybe more models (like 335iS, maybe 550iS, or 650iS?) are going to switch to DCT because of better fuel efficiency (mandate) and lighter weight.

I heard the first DCT failure cost $15,000 plus labor to replace. The last time I heard it's $9,500 plus labor to replace. Supply and demand dictate the cost of repair. Plus, if you're only talking about changing the clutch, it's a lot cheaper than replacing the entire unit.

As long as you don't abuse it everyday, following proper procedure BMW states that the DCT is good for the life of the car, not life of the warranty.

See http://www.motor-prime.com/content/m...h-transmission.
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      01-08-2013, 01:09 PM   #7
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Quote:
Originally Posted by e92M3C View Post
Common DCT failure rate is extremely low since its first debut on the M3. There is not enough data to gather.

By the way, the cost of repairing DCT has gone down significantly over the years due to the fact that more models are using it now. Eventually, maybe more models (like 335iS, maybe 550iS, or 650iS?) are going to switch to DCT because of better fuel efficiency (mandate) and lighter weight.

I heard the first DCT failure cost $15,000 plus labor to replace. The last time I heard it's $9,500 plus labor to replace. Supply and demand dictate the cost of repair. Plus, if you're only talking about changing the clutch, it's a lot cheaper than replacing the entire unit.

As long as you don't abuse it everyday, following proper procedure BMW states that the DCT is good for the life of the car, not life of the warranty.

See http://www.motor-prime.com/content/m...h-transmission.
Actually the M135i which has the new 8 speed is getting some good reviews, its performance seems to be similar to DCT. It might be that the next generation of automatics will be good enough for these cars, and DCT will remain a small niche.

See also this good recent piece from Chris Harris:

http://www.pistonheads.com/news/defa...?storyId=26917
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      01-08-2013, 01:21 PM   #8
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Just curious, do we have any documented DCT failure after the warranty period? Or is everyone dumping their V8s for the next gen M3/M4
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      01-08-2013, 02:28 PM   #9
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Quote:
Originally Posted by Leonardo629 View Post
Just curious, do we have any documented DCT failure after the warranty period? Or is everyone dumping their V8s for the next gen M3/M4
I don't think we have a definite documented failure. If there is it would be sticked to the thread.

All we have are isolated incidents (via extensive abuse) and the most famous is the DCT lag which was fixed by software update.
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      01-08-2013, 02:36 PM   #10
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Quote:
Originally Posted by sycd View Post
Actually the M135i which has the new 8 speed is getting some good reviews, its performance seems to be similar to DCT. It might be that the next generation of automatics will be good enough for these cars, and DCT will remain a small niche.

See also this good recent piece from Chris Harris:

http://www.pistonheads.com/news/defa...?storyId=26917
I would agree only if the manufacturers can somehow do away with the conventional power-eating torque converter. Seems like they are working on the idea right now, so essentially a hybrid between DCT and conventional automatic transmission. Maybe a wet-clutch type torque converter instead of fluid type?

http://www.europeantransmissions.com...ansmission.htm

http://www.dctfacts.com/emerging-tec...s-dct-bmw.aspx

Other than that, it still boils down to cost, supply and demand that dictates the wide availabiliy of the transmission type.
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