Can someone please educate me about Dual Mass Fly Wheels and what DSG means. Why have they got a bad name or have I simply heard bad things. Are they only on autos or are they on manuals too.
Have been looking at getting a VAG instead of one of the Terranos may be even a Roomster.
Dual Mass Flywheels are common in modern manual transmission cars to reduce noise, vibration and shock loads through the drivetrain. As opposed to a Solid Mass Flywheel whichis one solid plate, DMFs are two plates connected by dampening material (usually a mixture of springs and an oil filled cushion). One side of the DMF (and one plate) will be connected to engine and the other side (and plate) to the gearbox end of the drivetrain. As said they are only present in manual transmission vehicles
They're very effective and are used in some modern 4x4s (like Shoguns and Trols) to give them a more car-like drive.
The dampening section will deteriorate over time though and once it goes the two plates will start to rattle off each other, starting every so often when idling at operating temperature and progressively getting worse until it happens at idle all the time and then eventually the dampening section will go completely and you will lose all drive.
DMF wear is not helped by the fact that DMFs encourage lazy driving ie. less downshifting, as all the vibration is dampened so you don't get the feedback through the box from being in too high a gear. You may think everything is fine but the dampening section will be working overtime.
The problem with having them in big 4x4s like the 3.0 Trols is that the drivelines are especially beefy (the 3.0 Trol driveline is designed to handle the torque output of the big 4.2 diesel) and the 3.0 engine can, in an offroad situation, produce more power/strain than the DMF can handle. As the driveline is so beefy the DMF is the weak link and wear is accelerated.
Once the DMF goes a lot of Trol owners (like me) decide to forego fitting a new DMF and fit a solid flywheel instead, usually with a HD Clutch so that (fingers crossed) no-one has to be in there again for a long time :thumbs
The SMF and HD clutch combo also gives you a small torque boost :naughty
The SMF replacement is usually a bit more expensive than a new DMF but the upside is that it won't need replaced anytime soon if at all, unlike the DMF which will definitely fail (mine went around 85/90k but I have heard of some owners whose DMF failed sooner).
When the garage opened up the bell housing on mine to fit the SMF the inside was covered in oil from the dampening cushion having failed.
A SMF replacement does give a bit more drivetrain noise and it means you have to change your driving style a bit and change down more frequently but that's not a bad thing. It definitely gives you a feeling that there's a more solid connection between the engine and the drivetrain, which I like :thumb2
A point to note is that the 3.0 Terranos don't appear to have DMFs fitted (cncfabs confirmed when I was changing mine on the Trol), it's only the 3.0 Trol owners that got that privilege :doh
