The main question I've been trying to answer is: Is a DSG clutch less reliable than a standard clutch and by how much?

Which begs the questions:
As there are 2 clutches will each plate take 50% of the wear therefore the clutch will last twice as long as a standard clutch?

While one of the clutches is engaged will the other clutch be disengaged thus loading and wearing the throw out bearing thus dramatically reducing the life of the throw out bearing. (normally throw out bearings are only loaded when you press your foot on the clutch).

What happens when you come to a complete stop? There is no torque converter therefore the clutch plates have to slip or the clutch have to be disengaged when you put your foot on the brake and are at a full stop.

Does anybody have any information on how the actuation and control system works? I assume the gear shift is electrically actuated by motors?

Can you jump start the car if your battery dies?

Does anybody have any idea what how the system is broken down for repairs? Do you have to replace the whole unit or is it broken down into replaceable subassemblies

I've asked Audi technical support for information as a potential customer. They basically just sent me a cross sectional picture that doesn't help much.

Any information would be very much appreciated.

Thanks

Steve

 

The DSG is an hydraulic transmission--the two clutches are made up of multiple plates which are bathed in hydraulic fluid. They're hydraulically-actuated so there's no "throw-out bearing."

When you come to a complete stop (by applying the brakes), both clutches are then engaged, thus stopping transfer of power to the wheels, effectively shifting to "neutral."

The DSG shifts gears hydraulically, so the only motor is the hydraulic fluid pump.

You can jump-start a DSG-equipped car, but you can't "push-start" it--in that regard, it's similar to a standard automatic transmission.

 

Thanks for the info. Just out of curiousity where did you get your info? I've been looking for details.

One other question a colleague had that I couldn't answer well - how do they combine the two shaft outputs into 1? Is it done with another differential?

 

One output shaft is connected to 1st-4th gears.
The other has 5th & 6th + reverse.

 

"As there are 2 clutches will each plate take 50% of the wear therefore the clutch will last twice as long as a standard clutch?"

Yes, they each take about 50% of the wear.
But, 1st gear would normally cause most wear on a clutch.
But the clutches are different diameters (Bigger one is for 1st, 3rd, 5th).
But there is likely more shifting done if driven in "D".
But they are "wet" clutches (Less heat build up, possibly less wear).
But there are more parts to break/wear than a regular clutch.
But the hydraulic control is more steady/smooth than humanly possible for more even wear and elimination of accidentally burning/glazing the clutch.

But, but, but... The short answer is; Nobody knows. VAG sure is taking a big risk though since they will get an awefully lot of pissed off owners if these things need expensive clutch changes on a regular basis. My belief is that they've done the testing to know that it won't be a huge problem.

"Do you have to replace the whole unit or is it broken down into replaceable subassemblies"

IIRC, all repairs so far have been done under warranty and involved replacement of the entire transmission. However, from the pictures I've seen it looks like the clutch assembly is designed to be replaced separately since it is not internal to the transmission case. I would think that at some point clutch assemblies would be available. Worse case scenario is that you would just swap out the entire tranny for a rebuilt one.

 

<center><img src="http://webpages.charter.net/dwarner2/DSG_Animated.gif"></center><p>I'm looking at the cross section above. Found at:

http://webpages.charter.net/dwarner2/DSG_Animated.gif

and trying to work out how the clutch is actuated. Does the hydraulic pressure use the clutch housing in some way that it moves one set of clutch plates into contact at the same time moving the other set out of contact?

What happens in 'Park Mode'?

 

I'm looking at the cross section found here:
http://webpages.charter.net/dwarner2/DSG_Animated.gif

And trying to work out how the clutches are hydraulically actuated. My guess is that hydraulic pressure applied internal to one clutch forces the housing to separate disengaging one clutch and engaging the second.

Whe you releive the hydraulic pressure a spring returns the housing to engage the other clutch.

How does the 'Park Mode' work?

 

The pressure pushes a piston which is tensioned by a spring. When pressure is applied, the clutch closes and power flows though it. When the pressure is released, the spring opens the clutch and the input shaft is no longer connected.

The "Park" function is provided by a cable-operated lock on the differential gear.

 

Thus, it's possible to open both at the same time in order to either shift into Neutral or to come to a stop when the brakes are applied.

 

I thought one clutch was for even gears, the other for the odd number gears. This is what I thought allowed for the faster shifting. Does not make sense that one would be for 1-4 and the other 5,6 and reverse.