Valeoscope Commercial Vehicles Clutch 2020

Diagnosis Hard gear shifting

2.3 Verifications in

R 1 3

3

warm conditions (Manual gearbox only) Engine, oil and coolant temperature are in normal working conditions. ●● Same verifications as in cold conditions, ●● Clutch disc release (no sticking), ●● Disengagement travel: At clutch pedal At clutch release cylinder At clutch fork At release bearing At pressure plate (check according to truck manufacturer specifications) ●● Check the facing wear (to be done according to truck manufacturer method). Measuring the engaging time of reverse gear Conditions: ●● The vehicle is stopped. ●● Gearbox and clutch at usual operating temperature. ●● Engine at idle speed (check that the idle speed is within the manufacturer specifications). Measurement method: ●● Evaluate the necessary time to engage, without a scratching noise , the reverse gear or the 1 st gear if it does not have synchromesh (In warm conditions, the engagement time is longer than in cold conditions). ●● Proceed by successive steps starting with a very short time (1 second) or with the max acceptable time (7 seconds).

RECOMMANDED FOR MANUAL TRANSMISSION

2 4

Diagnosis

Example: ●● Declutch, wait 1s, engage the reverse gear = scratching noise ●● Declutch, wait 2s, engage the reverse gear = scratching noise ●● Declutch, wait 3s, engage the reverse gear = scratching noise ●● Declutch, wait 4s, engage the reverse gear = no scratching noise

3.1 Hard gear shifting 3.1.1 External reasons due to the gearbox or to the gearbox linkage (Manual gearbox)

Engagement time without a scratching noise in 4s = correct

Attention Ɂ Ɂ With some gearboxes (oil at operating temperature), it is sometimes necessary to wait until 7 seconds to be able to engage the reverse gear without any scratching noise. Advice   If the reverse gear engagement time (without scratching noise) is more than 7 seconds, it is considered as abnormal (the average value is 3 to 4 seconds).

Inertia of the friction Inertia of the first shaft Inertia of the synchronisation ring

Inertia of the second shaft

Engine

Clutch

Gearbox

Transmission shaft

Gearbox inertia

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