meade equatorial mount adjustment knob

I just picked up an old Meade complete 8" reflector and 115 volt drive mount for $50. No switches,just plug it in and drive works. My question is the only control on the drive is one knob, when turn it, it clicks like it's stripping gears. The knob goes directly into the motor gearbox so I quit turning it when I heard the clicking noise. Why is the knob there if not to be used, my logic says its a tracking fine tuning control but the clicking scares me. Any help would be appreciated.Thanks Bill