A dual-mass flywheel (DMF) serves two functions. The primary function is to store energy from each piston’s firing pulse, and then send it to the crankshaft so that it continues smoothly rotating through the next piston stroke. The secondary function is to dampen damaging torsional spikes caused by engine vibration. Historically, the disc serviced this function, however, complex transmission designs required an entirely new concept, well beyond the capacity of standard clutch disc technology.

Dual-mass flywheels were originally developed to reduce synchronizer wear, gear noise, and chassis rattle in high-torque diesel applications like 7.3L Ford and 6.5L GM trucks. However, because dual-mass

A DMF is basically two sections (primary & secondary) separated by springs or a viscous coupling. The primary section is attached to the engine while the secondary section is attached to the transmission (whenever the clutch is engaged). Two friction material facings (torque limiters) are incorporated into the DMF. They allow the secondary flywheel to slip relative to the primary flywheel, whenever the preset torque limit is exceeded. In addition, rubber pads are attached at various locations around the torque limiters. They cushion the impact of the two masses during start-up and shut-down cycles. The size and complexity of this system greatly increases the dampening effect at the transmission input-shaft, making driving more comfortable at any speed, increasing fuel efficiency, and reducing shifting effort.

Despite these advantages, dual-mass flywheels require periodic replacement because they are wear items that are sensitive to changes in engine torsional spikes (quite often resulting from damaged or plugged fuel injectors), bad valves and/or low engine compression. These issues will destroy either the DMF or the series dampened disc in as little as 3,000 to 10,000 miles. In addition, aftermarket accessories such as engine management chips or adjustable turbo waste gates significantly enhance horsepower and torque beyond the capabilities of the DMF. In many instances, it may be difficult to determine if the DMF has failed. That’s because the clutch, not the DMF, may be the cause of slippage. Finally, due to the fact that dual-mass flywheels are closely calibrated to the stock engine torque curves, they should not be resurfaced.

As an alternative to the high cost of DMF replacement in Ford and GM diesel powered trucks, AMS offers solid flywheel (SFW) conversions. These conversions are matched to an exclusive kit, which contains a series dampened disc that performs most of the dampening functions of a DMF. Most costs savings associated with the conversion come from the upfront savings, and the fact that solid flywheels can be resurfaced. Future clutch repairs do not then necessarily involve the cost of flywheel replacement.

Just like the DMF, the series dampened disc is ultimately designed to fail, in order to protect the transmission. However, when torque limiters on the DMF slip or fail, they still permit the DMF to transmit power to the transmission, allowing the vehicle to “limp” to a service area. By comparison, when the series dampened disc fails, the vehicle becomes powerless.

Several other disadvantages also exist. The series dampened disc does not dampen gear rattle as effectively as a DMF, thus creating