|If you experience the juddering mainly when you start the engine and when the car is idling, often accompanied by a loud clattering noise, the problem is likely in the dual mass flywheel which sits between the tran-smission and the engine. The flywheel consists of two plates that can move a small amount in relation to each other. This provides a cushioning effect when torque is transferred from the engine to the transmission. When that flywheel wears down, and the amount of move-ment is too great, you get a juddering/shuddering sensation.|
**NOTE: Before removing the DMF unnecessarily, you should also consider contaminated or corroded ground contacts, contact resistors on the electrical connections in the starter and generator electrical circuit as well as problems with the battery (insufficiently charged, damaged or defective) as a failure cause.
During a visual inspection, a discolored friction surface on the secondary flywheel (arrow A) indicates an overheated or overloaded DMF. This effect can occur if drivers let the clutch slip for too long or the release system is faulty. In addition, there is a danger that longer-lasting overheating will harden the special lubricant in the DMF, which frequently ends in component failure.
A DMF can also be checked while fitted in the vehicle or once removed using the special dual-mass flywheel test tool. Here, the free travel of the torsional damper, the evenness of its spring force, the axial bearing conditions and the displacement travel of the radial bearing site can be determined.
|When checking the free travel of the torsional damper, the secondary part of the DMF is rotated using the lever counterclockwise until encountering slight counterpressure or feeling the spring force of the torsional damper. The free travel should not be more than six teeth of the starter ring gear. If it is more than six teeth, it is highly likely that internal damage exists and the DMF will need replacing.|