Ownership / Clutch & Overdrive

Clutch & Overdrive

Many Stags left the factory as automatics, so the first thing to establish is which car you have — this article is about the manual car's clutch and overdrive; the automatic has no clutch to service.

Manual or automatic?

A large share of Stags were built with the Borg Warner automatic rather than the manual gearbox, and it is worth settling the question before you spend an afternoon under the car. The automatic has no clutch at all — it has its own fluid and servicing needs instead — so if yours is an automatic, everything that follows is background reading rather than a job list. Manual cars almost always came with Laycock overdrive on the upper gears, worked by a switch, and it is a feature well worth keeping healthy: it is the difference between a Stag that cruises and one that merely travels. If you are still deciding which car suits you, the transmission guide and the manual versus automatic comparison set out the two side by side.

The clutch

The manual Stag uses a single dry-plate clutch operated hydraulically, with a master cylinder at the pedal and a slave cylinder at the gearbox. It is a conventional arrangement, and conventional in its failings too — which is good news, because the diagnosis is usually straightforward if you take the complaints in the right order.

Hydraulics

A spongy pedal, dragging, or a clutch that will not fully release is most often the hydraulics — a tired master or slave cylinder, or fluid simply needing bleeding. Bleed the system and renew the cylinders as a pair rather than chasing one and then the other. This is frequently the real cause behind a "clutch" complaint, and a relatively cheap one: it is well worth exhausting before anyone reaches for the engine hoist.

Release bearing

A rumble or squeal when you press the pedal points to the release bearing. Because reaching it means removing the gearbox, do the whole clutch as a set — plate, cover and bearing — while you are in there. The bearing is a small part of the bill; the labour to reach it is not, and no one wants to do that job twice.

Slip

A worn friction plate, or oil contamination from a leaking crankshaft or gearbox seal, causes slip — engine revs rising without a matching increase in road speed. Cure the leak at the same time as fitting the new plate, or the fresh plate will be spoiled too, and quickly.

The overdrive

The Laycock overdrive is reliable when its oil is clean — it shares the gearbox oil — and its electrics are healthy. Overdrive that will not engage is more often an electrical fault than a failed unit: the switch, the wiring or the solenoid, or simply low oil. Check those first, and in that order, before condemning the overdrive itself; a great many "failed" overdrives have been revived by a clean connection or a topped-up gearbox. The electrical guide covers the earths and connectors behind faults of this kind, and the gearbox oil guide covers the level and the change.

Keeping it right

Fresh clutch hydraulic fluid, sound cylinders, and an eye on the overdrive electrics and oil level: that is very nearly the whole of it. Because renewing the clutch means removing the gearbox, do it thoroughly and once — plate, cover, bearing, and any leaking seal cured at the same time. Confirm specifications against the Stag workshop manual.