16 · Diagnostics

S20 Gearbox/differential unit noise general

Fault diagnosisS20 Gearbox/differential unit noise general

With the engine running and the vehicle moving, there is a noise from the area of the gearbox in all conditions.

Step	Test procedure	Result	Action
0	PRELIMINARY CHECKS Carry out a preliminary test to check the conditions which give rise to the noise	OK	General noise:Move onto step 1
		Noise during take-off	Move onto step (see S21)
		Noise in neutral	Move onto step (see S22)
		Noise in one gear only	Move onto step (see S23)
		Noise round bends	Move onto step (see S24)
1	GEARBOX/DIFFERENTIAL OIL LEVEL CHECK Check the gearbox / differential oil level Op. 2110A04	OK	Move onto step 2
1		Level too low	Restore the correct level End of diagnosis
2	CHECK GEARS Service the gearbox (SEE GEARBOX SERVICING Assembly 2110B) Op. 2110B32 In particular, check the gear teeth: they should not be worn or show traces of seizing	OK	Move onto step 3
2		Gears worn	Replace the gears involved End of diagnosis
3	CHECK SYNCHRONIZER RINGS Service the gearbox (SEE GEARBOX SERVICING Assembly 2110B) In particular, check the gear teeth: they should not be worn or show traces of seizing	OK	Move onto step 4
3		Seals worn	Replace the synchronizers End of diagnosis
4	REDUCTION TORQUE CHECK Check the crown wheel and pinion reduction gear (see OVERHAULING GEARBOXES Assembly 2110D) In particular: it should not be worn or damaged there should not be excessive clearance	OK	Move onto step 5
4		Reduction gear damaged	Restore the clearance or, if necessary, replace the reduction gear End of diagnosis
5	CHECK CORRECT OPERATION Check that the fault is no longer present	OK	End of diagnosis
5		Fault persists	Incorrect selection of diagnostic procedure

Parts & tools for this job For 1997 Alfa Romeo 156

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