Clutch kit

A clutch kit replaces the wear-prone components between the engine and gearbox with a single technically matched set. Depending on engine output, torque, flywheel type and transmission version, a kit consists of a clutch disc, clutch pressure plate and release bearing. The correct kit is always determined using the vehicle chassis number. Visual comparison, the outside diameter of the disc or selection based solely on the model name is never sufficient: splines, hub length, pressure plate depth, flywheel fitment and release system may differ within the same vehicle series.

Single-disc clutches, twin-disc clutches and clutches for NMV versions are available for MAN and Mercedes trucks, buses and vans. A single-disc clutch has one friction disc between the flywheel and pressure plate. This version is common in applications with suitable engine torque, for example with certain MAN D08 and D20 engines or Mercedes OM 904, OM 906 and OM 936 engines. The friction lining, torsional dampers in the hub and the clamping force of the diaphragm spring must match the permitted transmission torque.

A twin-disc clutch uses two clutch discs with an intermediate plate. Thanks to the greater available friction surface, this version can handle higher torque and thermal loads, such as in heavy tractor units with MAN D26, D38, Mercedes OM 471 or OM 473 engines.

An NMV clutch is also vehicle- and transmission-specific; therefore, determine the correct clutch kit using the chassis number. An incorrect disc thickness, hub splines or pressure plate can result in insufficient disengagement, slipping or damage to the input shaft.

Typical fault symptoms include rising engine speed without a corresponding increase in vehicle speed, a burning smell, juddering engagement, a heavy or pulsating clutch pedal and difficulty selecting gears. Slipping under load often indicates worn, glazed or engine oil- or hydraulic fluid-contaminated friction linings. Vibrations when pulling away can be caused by uneven lining wear, a warped intermediate plate in twin-disc clutches, defective torsional dampers or thermal cracks in the flywheel.

Measure the thickness of the friction linings and assess the rivet depth according to the manufacturer's specification. Check the flatness of the flywheel, pressure plate and any intermediate plate using a straightedge and feeler gauge; blue discoloration, heat checking or grooves are reasons to replace the relevant component. Also check the radial play of the pilot bearing, the axial movement of the release fork and the smooth operation of the release bearing. With hydraulic actuation, the master cylinder, clutch slave cylinder, lines and seals must be dry, and the release travel must be sufficient.

When a clutch is burnt or worn, preferably replace the complete clutch kit. Reusing a pressure plate or release bearing alongside a new friction disc presents a real risk of incorrect clamping force, noise or premature failure. Clean flywheel contact surfaces only with a suitable degreaser; grease, assembly paste or engine oil on the linings will cause immediate slipping. Centre the discs with suitable centring tools and use new mounting bolts where specified. Tighten the pressure plate crosswise to the specified tightening torque.

Always investigate the source of contamination: a leaking crankshaft seal, gearbox input shaft seal or defective hydraulic release system can quickly damage a new kit. For technically correct selection and reduced downtime, chassis number verification and technical support from Braem can help determine the appropriate single-disc, twin-disc or NMV clutch kit.