Fault diagnosis	manual gearbox
	Note: It is sometimes difficult to decide whether it is worthwhile removing and dismantling the gearbox for a fault which may be nothing more than a minor irritant. Gearboxes which howl, or where the synchromesh can be 'beaten' by a quick gear change, may continue to perform for a long time in this state. A wom gearbox usually needs a complete rebuild to eliminate noise because the various gears, if re-aligned on new bearings, will continue to howl when different wearing surfaces are presented to each other.
	The decision to overhaul, therefore, must be considered with regard to time and money available, relative to the degree of noise or malfunction that the driver can tolerate.
Symptom	Reason/s
Gearbox noisy in neutral	Worn transfer gears or idler gear bearing (noise stops when clutch pedal depressed)
	Layshaft bearings worn
Gearbox noisy in all gears	One or both of above faults General wear
Gearbox noisy in one particular gear	Worn, chipped or damaged gear teeth
Gearbox jumps out of gear on drive or overrun	Detent balls and springs worn
	Coupling dogs worn
	Selector forks worn or rods loose
	Worn synchro hubs or baulk rings
Crunching or crashing when changing gear	Clutch fault (see Chapter 5)
	Worn baulk rings or synchro hubs
Difficulty in engaging gear	Clutch fault (see Chapter 5)
	Gearchange linkage worn, loose or maladjusted