slk55er

So do our DCT transmissions contain one or more traditional clutch discs with friction material that will eventually need to be replaced? Ultimately, after say, hundreds of Race Starts, what will be the first part in the transmission that will have to be replaced? After how many miles would that likely be required in "normal" driving (if that is possible in a GT model)?

slk55er

Hmm. No answers or replies. Maybe a stupid question, but surely someone on this forum know a a lot about our DCTs.

guynamedsean

Fwiw I've never heard of a dct wearing out in a stock porsche, BMW or Benz

DragonRR

According to most sources the AMG GT series have an amg speedshift dct 7-speed transmission.


I'm guessing this is probably a modified version of the 7G DCT: It looks similar.

http://techcenter.mercedes-benz.com/...ct/detail.html

slk55er

Thanks much. The video shows what appear to be multiple discs in both clutches, but who knows if these are wear out items?

guynamedsean

I'm sure if you keep the vehicle long enough outside of the warranty period, it will eventually need servicing and be expensive. I think most buyers of these cars don't keep them outside of warranty though.

slk55er

Yes, although I hope to keep mine longer. Perhaps the discs that I see in the video are running in transmission fluid and have vanes as in a torque converter or auto transmission, never making contact with each other or the equivalent of a flywheel and pressure plate.

guynamedsean

I think dual clutch means one clutch is for odd gears and the other is for even gears. I think this plus the fact that it's computer controlled lowers wear.

DragonRR

AFAIK DCT transmissions generally use multi-plate friction based clutches, they will wear out eventually but since they are entirely electronically controlled they are likely to last a very long time:

This is copied from the source here:

http://auto.howstuffworks.com/dual-c...nsmission1.htm



Multi-plate Clutches

Because a dual-clutch transmission is similar to an automatic, you might think that it requires a torque converter, which is how an automatic transfers engine torque from the engine to the transmission. DCTs, however, don't require torque converters. Instead, DCTs currently on the market use wet multi-plate clutches. A "wet" clutch is one that bathes the clutch components in lubricating fluid to reduce friction and limit the production of heat. Several manufacturers are developing DCTs that use dry clutches, like those usually associated with manual transmissions, but all production vehicles equipped with DCTs today use the wet version. Many motorcycles have single multi-plate clutches.






Like torque converters, wet multi-plate clutches use hydraulic pressure to drive the gears. The fluid does its work inside the clutch piston, seen in the diagram above. When the clutch is engaged, hydraulic pressure inside the piston forces a set of coil springs part, which pushes a series of stacked clutch plates and friction discs against a fixed pressure plate. The friction discs have internal teeth that are sized and shaped to mesh with splines on the clutch drum. In turn, the drum is connected to the gearset that will receive the transfer force. Audi's dual-clutch transmission has both a small coil spring and a large diaphragm spring in its wet multi-plate clutches.
To disengage the clutch, fluid pressure inside the piston is reduced. This allows the piston springs to relax, which eases pressure on the clutch pack and pressure plate.

slk55er

Excellent! Thank you DragonRR. Very helpful.

smrtasp

I was trying to also understand the life of a DCT when I started looking at the GT. Over on M5Board.com a BMW tech had posted in one of the M3 forums that the expected life of a DCT, minus excessive track use or some other mechanical failure that would require replacement, was expected to be in the 150K mile range. I had an older M5 with the SMG and a Gran Tourismo with the F1 and I absolutely didn't want that type of experience again. DCT should be the standard in all performance cars at this point.