Pinpoint Test F: Clutch-Related Vibrations

Manual Transmission and Clutch






Pinpoint Tests

Pinpoint Test F: Clutch-Related Vibrations

Normal Operation

The clutch is designed to transfer the power from the engine to the transmission, which may be either stationary (starting) or rotating at a different speed (upshifting or downshifting). The clutch is functioning correctly when both the engine and transmission are rotating at the same speed with the clutch engaged. Clutch pedal movement is transmitted by fluid pressure, which actuates the clutch release hub and bearing. The clutch release hub and bearing pushes on the spring center towards the flywheel. The diaphragm spring pivots at the fulcrum, relieving the load on the clutch pressure plate. Steel spring straps riveted in the clutch pressure plate cover pull the clutch pressure plate from the clutch disc, disengaging the engine torque from the transmission.

This pinpoint test is intended to diagnose the following:
- Engine components
- Accessory drive belts
- Release bearing
- Flywheel



PINPOINT TEST F: CLUTCH-RELATED VIBRATIONS

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F1 CHECK FOR ENGINE COMPONENT GROUNDING


- With the vehicle in NEUTRAL, position it on a hoist. Refer to Maintenance/Service and Repair.
- Check the engine and transmission mounts for grounding.
- Check for exhaust manifolds or other engine component grounding on the body or frame.
- Is there evidence of grounding on the body or frame?

Yes
REPAIR the components as necessary. TEST the system for normal operation.

No
GO to F2.

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F2 CHECK FOR ACCESSORY DRIVE VIBRATIONS


- Start the engine.
- Remove the accessory drive belt.
- Does the vibration stop when the accessory drive belt is removed from the engine?

Yes
REFER to Drive Belts, Mounts, Brackets and Accessories to diagnose the accessory drive belt components.

No
STOP the engine and INSTALL the drive belt. GO to F3 .

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F3 CHECK FOR CLUTCH RELEASE BEARING NOISE


NOTE: With the transmission in NEUTRAL, transmission rollover noise can be heard. Make sure to distinguish between rollover noise and clutch release bearing noise.

- Start the engine.
- Depress and hold the clutch pedal.
- Is a whirring, grating or grinding noise present only when pedal is pushed?

Yes
INSTALL a new clutch release bearing.

No
GO to F4.

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F4 INSPECT THE FLYWHEEL


- Ignition OFF.
- Remove the transmission.
- Carry out a flywheel check. Refer to Flywheel Runout Check Flywheel Runout Check.
- Is the flywheel OK?

Yes
VERIFY customer concern. GO to Symptom Chart if necessary. Symptom Related Diagnostic Procedures

No
TIGHTEN or INSTALL a new flywheel. TEST the system for normal operation.

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