Clutch brake adjustment is really a bi-product of clutch adjustment . If the clutch itself is in good condition and the free travel etc is correct , the clutch brake should work if it is not worn out . When the yoke pulls back on the throwout bearing , which has a flat face on it , it pinches the clutch brake disc between itself and the flat face on the front of the box . The brake disc being splined to the input shaft stops the shaft to allow a gear to be selected . You can buy a hinged brake disc that can be fitted with the box in situ . Once the old one is air chiseled out , the new one is fed around the shaft and locked together with a pin . People over clutching cause most of the wear . If a clutch is used at all whilst driving , it should only be pushed in about half way , just enough to make the pressure plate let go . Pushing all the way to the floor has the clutch brake trying to slow the main shaft at highway speeds .