How do you tell if the Gearbox thrust bearing is broken?

Answer 1

Could be a long list of things;

Noisy when clutch pressed

Pulsating pedal with engine running

Difficult to ingage gears

Slipping clutch or harsh vibrations

The thrust bearing, and fork, should be replaced when the clutch is replaced.

Bearing Slide and Fly wheel should be inspected and replaced if need be.