LuK INA FAG Products Services News

Se r v i c e . P owe r. P a r t n e r s h i p . Schaeffler Automotive Aftermarket (UK) Ltd

Holme Lacy Road, Rotherwas,Hereford HR2 6BQ 01432 264264A Member of the Schaeffler Group of Companies

50% of UK vehicles are now fitted with Dual Mass Flywheels(DMF) and Damped Flywheel Clutches (DFC). These areessential components that not only provide an enhancedlevel of driveability but also reduce harmful torsionalvibration that would otherwise be transmitted into thegearbox and driveline.

It is essential that you check the DMF/DFC (the procedureis the same for both) during every clutch replacement - ifyou fit a new clutch to a worn DMF/DFC, the flywheel willcompletely destroy it !! Solid Flywheel alternatives canalso lead to severe and expensive damage to gearbox anddriveline components.

If the customer complains of any unexplained noises,vibration or intermittent clutch slip it could be caused bya worn DMF.

Testing procedure

Dual Mass Flywheel diagnosis Expert advice

Check the Flywheel for...

• Friction face scored• Overheated/blueing• Stress cracks• Grease loss

Step OneFirst listen for…

• Rattles and clonks duringengine start up or turn off

• Excessive gear rattle• Unusual noises

Step TwoAfter removing the clutch fromthe vehicle check the clutch for…

• Driven plate damage• Drive strap damage

Step Three - Freeplay

With the Flywheel still fitted...

• Rotate the secondary mass anti-clockwise until spring pressure can be felt, then allow it to return

• Zero the Special tool gauge or mark the position of the secondary mass relative to the ring gear

• Do the same in a clockwise direction, mark the flywheel position again count the ring gear teeth between the marks or read off the freeplay angle from the Special Tool

To check the bearing or bush for wear...

• Gently measure the amount of rock at the outer edge of the secondary mass or on the Special Tool adaptor with a DTI (included in the Special Tool kit)

Replace if movement is...

• More than 1.6mm for a roller typebearing

• More than 2.9mm for a bush typebearing

LuK Technical Hotline: 08457 001100

Measuring Freeplay with theSpecial Tool

Friction Control devices will restrict the Freeplay movement. The DMF Special Tool is designed to overcome this device.

When rotating the secondary mass if a hard stop can be felt beforethe spring in either direction, continue to rotate the secondarymass a few millimetres at a time until the spring can be felt, thenallow it to return. At this point you can either set the zero on thegauge or read off the Freeplay.

DMF with Friction Control Device

Measuring the Freeplay and the Rock are an indication of thecondition of the flywheel when tested.

The DMF should be replaced if the Rock or Freeplay limits areexceeded or if there is evidence of...

• Excessive grease loss • Friction face damage• Any unusual noises are reported • Clutch damage

Further consideration should be given to... How the vehicle is used or (abused) and whether the DMFwill last another clutch duty cycle.

Step Four - Rock

Maximum Freeplay and Rockvalues can be found on

• www.repxpert.com

• www.schaeffler-aftermarket.com

Measuring Freeplay withoutthe Special Tool

Measuring Rock

Freeplay angleFriction controlplate limiting

Freeplay

LuK Special Tool - LuK Part No. 400008010

DMF_a2_tool_poster_DMF_a2_tool_poster 30/03/2012 15:15 Page 1