457
Solving
a problem with an LH overdrive cycling in and out
A fault experienced
by some MGB and V8 enthusiasts with a Laycock LH overdrive unit is that when the
multi-function stalk switch has been operated to engage overdrive, the overdrive
then begins to cycle in and out - engaged and disengaged and engaged again - and
continues to do so as the car is driven at a steady speed. The essential question
is "what can cause an overdrive to malfunction and how do you cure it?"
Here Victor Smith with contributions from fellow V8 members address that question.
(Nov 12)
The likely causes for an
overdrive cycling in and out are a faulty overdrive inhibitor switch, a low oil
level in the gearbox, an ageing seal causing an oil pressure leak, a faulty seating
for the valve ball bearing, a faulty multi-function stalk switch operating the
overdrive or an electrical fault related to the solenoid. Generally it is more
likely the fault will be electrical, but two of the early steps in the diagnosis
are to check the inhibitor switch and the oil level. |
Drain plug (1), Cover (3), Filter & gasket (4), Magnets
(5), Relief valve filter plug (6), Sealing washer (7), Relief valve (8), Filter
(9), Seal (10) and Combined filler & oil level plug (11).
See an illustrated five page note which covers each of the likely causes
with notes on how to make the checks, explains how the overdrive unit works and
has an exploded diagram of the overdrive as a useful guide. V8NOTE457 |
