Do you need a new clutch for your TDI?  In this article we outline and compare differences between flywheel options so you can make an informed decision for your car.

Single Mass  Flywheels

An SMF, or single mass flywheel, is made out of a single cast piece of steel, has no moving pieces and cannot break or fail.  This is the traditional design for most flywheels that are nothing more than a rotating mass of metal.  Pretty much every vehicle built before the year 2000 used a single-mass type flywheel – before the dual-mass flywheel was invented and before we needed to specify single-mass versus just stating “flywheel.”

Single-mass designs have a few downsides which created the need for dual-mass designs. Single mass flywheels have no internal damping mechanism, so engine vibrations are transmitted from the crankshaft into the transmission. This causes gears in the transmission to “rattle”.  Although this sound is not indicative of a problem it doesn’t sound especially good. Secondly, along with these vibrations, engaging and disengaging single-mass clutches is much less smooth, exhibiting more “jumpy” or “jerkiness” during engagement. Finally, as engine load increases the power pulses can be transmitted into the vehicle.

Dual Mass Flywheels

The name “Dual-Mass Flywheel” refers to the fact that the flywheel is made up of multiple pieces. There are two main pieces, the inner damper and the outer damper. These two pieces are connected using a complicated set of inner springs and an “arc spring” which goes around the outside edge of the flywheel.

This system dramatically smooths the power delivery from the engine to the transmission. It solves the gear-rattle issue, makes engagement and disengagement silky smooth and prevents the vehicle chassis from vibrating during acceleration.

However, like anything complicated, dual mass flywheels are prone to failure. The most dangerous failure of a dual mass flywheel is when the inner and outer dampers separate. This can lead to immediate power loss and catastrophic damage to the transmission. Before this occurs, however, dual mass flywheels will start to produce loud “clanking” noises on start up and shut down. If you noticed these noises you should bring your vehicle to a mechanic soon and anticipate a clutch replacement.

Choosing a Replacement – Single vs Dual

The hard fact is that a single-mass flywheel is more reliable than a dual mass design. While dual mass flywheels can last 100,000 miles or more, there is no real limit to how long a single mass flywheel can last. If your TDI needs a replacement clutch, we recommend investigating single-mass conversion clutch kits before making a purchase.