CHASSIS NOISES.

Evening Post, Volume CXI, Issue 121, 22 May 1926, Page 17

CHASSIS NOISES.

Chassis noises may be divided into a number of classes —squeaks, rattles, knocks, and growling or grinding sounds.

Much can be done by the application of common-sense towards finding out what parts are causing the noise. The best way is first to localise any elusive sound by ascertaining whether it is heard when (a) the engine only is running, (b) ths car is moving, or (c) in the case of (b), on what gear it is heard most frequently. Obviously, if the sound is heard when the car is stationary and the engine running, the noise must bo'either in the engine or between it and the lay shaft of the gearbox. An intermittent

squeak may be caused by a dry clutehwithdrawal mechanism, and a rattlo or grinding sound may indicate a worn or damaged clutch-withdrawal race. Whether the latter is the case can often bo confirmed by placing the foot lightly on the clutch pedal and observing whether it moves up and down or vibrates. If an untoward sound seems to come from the engine or the transmission on the road, its origin can often be traced by observing whether it continues, •while the car is still moving, if the clutch pedal is suddenly depressed or the gear lever is slipped into neutral. Again, if the source of the noise is in the engine and gearbox, it will be multiplied, assuming that a constant road speed is maintained, on the lower gear ratios. For instance, where the top gear is 4 to. 1, and second speed is 8 to 1, any engine or clutch noises will be double at 20 miles per hour on second gear what they are at 20 miles per hour on top gear. By the same process of deduction, it is often possible to find out what is the cause of an engine noise, if it is observed whether it coincides with the upward or downward motion of a particular valve or piston.