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      12-02-2012, 06:45 PM   #61
RPM90
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Drives: 335i Msport w/sport AT
Join Date: Mar 2006
Location: Chicago

Posts: 6,063
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Quote:
Originally Posted by gthal View Post
I agree with this (other than the comment that a DCT is crap in traffic because it isn't and is actually fairly smooth)... I believe the M-DCT might be faster (could be wrong) but at the speed in which they both operate it would be irrelevant. I also do agree that the 8AT is easier to live with day-to-day. The MCT transmission in the C63 is also very fast shifting (quoted at 100ms) which is likely similar to the M-DCT but it is no where near as "connected" or fluid in manual mode as the DCT.

A DCT's advantage is its feel and connection with the car in manual mode and that is the only area where no AT can really compare. The DCT feels and acts like a true manual (because it is) and feels like a direct link to the car. In manual mode and in aggressive driving it is incredibly fun in a way an auto can't match yet. Driving around town, this connection and responsiveness is much less relevant and the DCT isn't as good in those circumstances for sure.
Having driven VW's DSG, and the S4's 7spd "DSG", compared to the ZF sport AT, I agree that there is a difference in "feel" and connection.
Tightest feel goes to the dual clutch. Smoothness goes to the ZF, especially in day to day driving.

Now, after posting all my praises for the ZF sport AT, my AT needs to be looked at. It's acting funny.
When it's cold manual shifts are harsh and abrupt. Even after the engine and trans are very well warmed, manual shifts are not as smooth as they are in auto mode.

Today I got some very odd trans behavior and frankly kind of dangerous.
I was doing some tests of the trans and I got it to do an 8th to 2nd downshift amazingly fast. It was during accel. I was between 40-45mph trans was in AT in 8th. I stomped the throttle to the floor it kicked down to 2nd and took off like a rocket. LOVE the 3.0 turbo.

Then I let things cool down and drove around in comfort auto mode.
I switched to manual and was coming to a stop light. I down shift to 4th it's ok, then 3rd, but it was NOT smooth at all. The trans shifted to 3rd and the car JUMPED forward very aggressively, then I went to 2nd and it did the same thing, JUMPED forward hard. Luckily there was no one in front, but if there were I could have hit their bumper if I wasn't fast on the brake.
I tested this out a couple more times and it did the same thing.
It never did this before.
I went shopping and then came back, started it up, drove, repeated the same test and the downshifts were smooth and rev matched as the should be.

It felt like the "rev matching" wasn't working at all. I select a down shift to 3rd and it goes then lurches hard forward, not good.
I've been wanting to take it in for a few weeks now, but without any codes I'm sure I'll just get the "no problems found" conclusion.
Since trans performance seems to be getting worse I may hold out until something happens. I'll be on vacation around Xmas and won't be going out of town. If this happens again I'm going straight to the dealer, not shut the car off and have the service writer go for a drive.
Hopefully I can repeat the problem.
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