A gearbox-out clutch change is one of the larger workshop jobs an owner of a classic MG takes on, and the right tools transform it from a frustrating problem into a satisfying day's work. The principal challenge is the clutch-plate alignment, getting the friction plate centred on the flywheel so the gearbox input shaft can pass through it cleanly when the gearbox is mated back to the engine, as a misaligned clutch plate is the single most common reason a gearbox refuses to engage with the engine on reassembly, leaving an awkward and time-consuming problem to resolve under the car.
Clutch-Plate Alignment Mandrels
A clutch alignment tool is a stepped or splined mandrel that locates the clutch plate centrally on the flywheel during pressure-plate fitment. The small end of the tool enters the spigot bush in the centre of the flywheel or crankshaft, the centre section locates inside the splined centre of the clutch friction plate, and with the tool in place the pressure plate can be bolted down with the plate held precisely centred, so that when the tool is withdrawn the plate stays in position and the gearbox input shaft slides in cleanly. The mandrels are matched to the diameters and splines used across the classic-MG range, and the correct tool is specific to the engine and the spigot bush actually fitted, so it should be confirmed before ordering. On the MGB, separate tools cover the three-main-bearing 18G and 18GA engines and the five-main-bearing 18GB onwards engines, which differ in spigot bush diameter, the MGC tool also fitting the MGB from 1965 onwards as both share the same spline and spigot bush specification, and on the Midget two spigot bush diameters were used on the 1275cc and the 1500cc has its own distinct specification, so the bush in the engine should be checked before ordering.
Spigot-Bush Pullers & Flywheel Locks
The spigot bush or pilot bearing in the centre of the flywheel or crankshaft supports the front of the gearbox input shaft, renewed during a major clutch overhaul, and a puller is needed to extract the old component without damaging the flywheel, typically a slide-hammer pattern with grip jaws that engage the inside of the bush and work against the flywheel face to draw it straight out. A worn spigot bush allows the gearbox input shaft to wobble, causing the clutch plate to wear unevenly and generating a rumbling noise with the pedal depressed, so it should always be checked when the gearbox is out. Flywheel-locking tools, typically a forked bar that engages the starter ring gear and braces against the engine block, hold the flywheel stationary while the centre bolt is torqued during assembly, as without the lock the engine turns over against the wrench making accurate tightening impossible.
Spring Compressors & Related Tools
A clutch spring compressor holds the diaphragm spring compressed during clutch cover removal and refitting, and a clutch plate inspection gauge checks the friction material thickness to determine whether the plate can be reused. When the gearbox is removed for clutch replacement, several related items should be inspected and renewed as a matter of course, as they are only accessible with the gearbox out and their failure would require the entire removal process to be repeated, the release bearing, release arm bush, and gaiter being inexpensive items that are sensible to replace at the same time. Clutch slave-cylinder pushrod adjustment matters on cars where it is required, as too short and the clutch will not fully disengage when the pedal is pressed, leaving a gearbox that crunches into first, and too long and the clutch will not fully engage when released, leading to slip and accelerated wear, while the brake-bleeding kits in the Brake Tools section are appropriate for bleeding the clutch hydraulic line on cars where the clutch shares fluid specification with the brakes.