It you have an inch or more movement on the clutch pedal before you can feel the pressure plate springs it needs to have a bearing adjustment. This adjustment can only be done with the transmission split away from the torque tube. There is a cover over the adjustment nut. That nut is staked and after the adjustment is made it will need re staked. This shaft runs on tapered bearings and when you have wear they become loose and causes free wheeling of the shaft and gears. It needs to be tight enough that it has some drag. If you get it to tight it will cause bearing failure.
A tight pilot bearing on the drive shaft can also cause this gear grinding problem as well. Not as likely but can happen.