Clutch System Description and Operation C6500, C7500, C8500

There are 3 different clutch assemblies used on this vehicle, depending on the engine application and the transmission. In order to perform the proper diagnosis and the correct repairs, it is important to understand which clutch assembly is being used and how it operates. The following components make up the clutch system:

Clutch Brake : The clutch brake is a disc, with friction material, that is tabbed to the input shaft. It is squeezed between the release bearing and the transmission front cover during clutch disengagement, to stop the rotation of the input shaft. It is used with non-synchronized transmissions to allow shifting into a gear while the vehicle is not moving.

Clutch Cable : The clutch cable transfers the clutch pedal motion to the clutch lever. The cable has adjustable ends for positioning the release yoke or fork.

Clutch Cover: The clutch cover is part of the pressure plate cover assembly. It retains the springs and other levers that operate the pressure plate. The clutch cover is bolted to the flywheel.

Clutch Disc: The clutch disc is referred to as the driven member. It is a flat plate that may have damper springs. Depending on the clutch assembly, it may have either 3, 4, or 6 paddles. The friction material located on the paddles is clamped between the flywheel and the pressure plate. The disc hub is splined on the input shaft and delivers the engine torque to the transmission. Different friction materials are used to give smooth and long lasting clutch operation. For increased engine torque applications, two discs are sometimes used.

Clutch Lever : The clutch lever connects the clutch cable to the clutch cross shaft.

Clutch Pedal: The clutch pedal is mounted in the cab on a bracket. It is operated by foot pressure, swivels on a shaft, and assisted to the upright position by a spring.

Clutch Pedal Free Travel: The clutch pedal free travel is the amount the pedal moves before the clutch release bearing moves.

Clutch Pressure Plate: The clutch pressure plate is referred to as the driving member. It has a steel disc, with a machined surface, that is forced against the clutch discs by the springs in the clutch cover.

Clutch Pressure Plate Cover Assembly : The clutch pressure plate cover assembly consists of the pressure plate, the cover, and the springs that apply the clamping force to the clutch discs.

Clutch Release Bearing: The clutch release bearing is attached to the clutch pressure plate on some applications or it may slide on the transmission quill tube. It moves the springs in the pressure plate to release the clamping load. The bearing may require routine lubrication or may be a sealed style.

Clutch Release Yoke: The clutch release yoke rotates with the cross shaft. It has fingers that move the clutch release bearing.

Cross Shaft: The cross shaft is a two piece shaft that goes through the clutch housing and is supported by bushings. The clutch release yoke fastens to the cross shaft.

Pull Type Clutch : With the pull type clutch, the release bearing is pulled away from the pressure plate cover assembly during clutch disengagement.

Push Type Clutch: With the push type clutch, the release bearing is pushed towards the pressure plate cover assembly during clutch disengagement.

This vehicle uses a clutch cable to operate the clutch system. Movement from the clutch pedal is transmitted to the clutch lever and linkage through the clutch cable. Different configurations of linkage rotate the release yoke, depending if the clutch assembly is a pull type or a push type.

RPO MPJ

The clutch assembly manufactured by Valeo is used with the 8.1L engine. The clutch is a 330.2 mm (13 in) push type, 4 paddles. A clutch yoke that pivots on a cross shaft in the clutch housing, is used to move the release bearing, which slides on the transmission quill tube. Adjusting the clutch cable moves the clutch yoke for the proper clutch adjustment.

RPO MPM

The clutch assembly manufactured by Valeo can be used with the Duramax 7.8L and the Caterpillar 7.2L engine applications. The clutch is a 355.6 mm (14 in) with a single cerametallic disc, 6 paddles. The clutch operation is a diaphragm spring pull type. The clutch may be used with a clutch brake.

RPO MPK

The clutch assembly manufactured by Eaton Fuller is used with the Duramax 7.8L and the Caterpillar 7.2L engine applications. The clutch is a 355.6 mm (14 in) with 2 ceramic discs, 3 paddles each. The clutch operation is pull type. It is self-adjusting and referred to as the Eaton Solo®. Sliding cams in the pressure plate cover assembly move the pressure plate as the clutch discs wear. The clutch may be used with a clutch brake.

Clutch System Description and Operation C4500, C5500

The clutch used with the 8.1L and the 6.6L engines is RPO MPJ. The clutch is a 330.2 mm (13 in) single disc Valeo push type clutch. The following components make up the clutch system:

Clutch Cable: The clutch cable transfers the clutch pedal motion to the clutch lever. The cable has adjustable ends for positioning the release yoke.

Clutch Cover: The clutch cover is part of the pressure plate cover assembly. It retains the springs and other levers that operate the pressure plate. The clutch cover is bolted to the flywheel.

Clutch Disc: The clutch disc is referred to as the driven member. It is a flat plate that has damper springs. The friction material located on the paddles is clamped between the flywheel and the pressure plate. The disc hub is splined on the input shaft and delivers the engine torque to the transmission. Different friction materials are used to give smooth and long lasting clutch operation.

Clutch Lever : The clutch lever connects the clutch cable to the clutch cross shaft.

Clutch Pedal: The clutch pedal is mounted in the cab on a bracket. It is operated by foot pressure, swivels on a shaft, and assisted to the upright position by a spring.

Clutch Pedal Free Travel: The clutch pedal free travel is the amount the pedal moves before the clutch release bearing moves. With the clutch system operating correctly, there should not be any clutch pedal free play.

Clutch Pressure Plate: The clutch pressure plate is referred to as the driving member. It has a cast iron disc, with a machined surface, that is forced against the clutch discs by the springs in the clutch cover.

Clutch Pressure Plate Cover Assembly : The clutch pressure plate cover assembly consists of the pressure plate, the cover, and the springs that apply the clamping force to the clutch discs.

Clutch Release Bearing: The clutch release bearing slides on the quill tube of the transmission. By the rotation of the clutch release yoke the clutch release bearing moves towards the levers in the pressure plate to release the clamping load.

Clutch Release Yoke: The clutch release yoke rotates with the cross shaft. It has fingers that move the clutch release bearing.

Cross Shaft: The cross shaft is a one piece shaft that goes through the clutch housing and is supported by bushings. The bushings require lubrication for proper operation. The clutch release yoke fastens to the cross shaft.

Push Type Clutch: With the push type clutch, the release bearing is pushed towards the pressure plate cover assembly during clutch disengagement.

This vehicle uses a clutch cable to operate the clutch system. Movement from the clutch pedal is transmitted to the clutch lever and linkage through the clutch cable. The clutch lever rotates the release yoke on the cross shaft in the clutch housing. The release yoke moves the release bearing forward or pushes against the levers on the pressure plate assembly to disengage the clutch.

Proper placement or adjustment of the release bearing is critical for correct clutch operation. If the release bearing is too far from the release yoke, it may prevent complete clutch disengagement. If the release yoke is adjusted too tight to the release bearing it may cause release bearing failure or clutch slippage.

Pedal Reserve

In order for the clutch to be completely disengaged and allow proper shifting of the transmission, clutch pedal reserve is required. Clutch pedal reserve is the movement of the pedal from the downstop (1), the floor, or the clutch brake to where the clutch begins transmitting torque (2). It should be a minimum of 25 mm (1 in).