Quick gearbox question

[scottyp123]

A clutch fork doesn't move but the clutch assembly spins round so to join the two together a thrust release bearing is used. However inside the gearbox all the gears spin round and so do the selectors but obviously the selector forks don't, so what stops the forks from wearing out, especially as it must place a bit of pressure on them when they are actually selecting a gear?

[GreenV8S]

It comes down to how much force the bearing has to carry.

The clutch takes a very high force to unload the pressure plate - many times more than the force you apply to the pedal.

The gearbox takes almost no force to move a synchro hub into engagement.

[scottyp123]

Even with no force though they are still touching and some forks are made out of ali. Is there no bearing between them.

[InitialDave]

They're in oil, remember.

[GreenV8S]

That's why it's bad practice to drive with your hand leaning on the gear lever - although the force is relatively low, if you keep pressing it in or out of gear it will eventually cause wear on the selector forks.

[oakdale]

scottyp123 said:

Even with no force though they are still touching and some forks are made out of ali. Is there no bearing between them.

The springs and balls in the sliding syncro hub hold the hub firmly in the neutral or in gear position, the detent plungers and springs do the same with the selector rods or rail, so there is no thrust force on the forks other than when changing gear.