|Clutch judder in old car
Question : I DRIVE a 1975 Nissan (Datsun) 120Y that my
mechanic says is suffering from clutch judder. As a consequence, my mechanic had
also advised that the entire clutch mechanism
should be renewed as soon as possible. I would
appreciate an explanation of what "clutch judder" is, what causes clutch judder and how it
can be rectified.
CLUTCH judder refers to the vibration that is
felt throughout the vehicle chassis at the point
when the clutch takes up drive. Often the sensation is a violent vibration, so aptly described as a
judder. The clutch is a mechanism used to gradually apply engine power to the driving wheels.
The clutch consists of two friction surfaces that
are gradually brought together so that as the friction between the two surfaces is gradually
increased, the amount of power transmitted is
also increased as a result. Eventually sufficient
pressure is applied to both surfaces that no more
slip occurs and all engine power is transmitted to
the driving wheels.
The clutch consists of three major components
-- the clutch beating, pressure plate and the friction plate. The bearing bears on the pressure
plate; the job of the latter is to gradually apply
pressure on the surfaces of the friction plate and
Judder occurs when one or more of the clutch
components have worn, failed or become misaligned. When this happens, "slip" is
not constant, but rather the surface of the friction plate engages the
flywheel at certain points along its periphery, hence creating the juddering
A similar juddering action occurs if the components e.g. the layshaft of the gearbox becomes
misaligned, or if the flywheel is distorted.
Although clutch components are available separately, and indeed may be
renewed separately, it is often inadvisable to do so since there is a considerable amount of labor involved in gaining
access to the clutch components. For a start, the
gearbox must be removed, and in certain cases,
the engine along with the gearbox must be
removed from the vehicle as a complete assembly.