There is a single ball in the brush plate above the top of the armature shaft. It handles vertical up thrust caused by the worm. This is the ball that is so frequently lost. You might want to unsolder the field wires so they do not get broken off. I like to take the field assy. off the frame to give better access to the worm gear on the axle, which is probably coated with stiff sticky old grease. I clean the old grease out of the gear housing with q-tips, off the sides of the gear with an xacto knife and out of the gear teeth with a tooth pick.
With the armature out the geared axle should turn freely. Try turning it while pushing the wheel toward the frame. It should still turn fairly freely. If it binds, the wheel is probably rubbing the frame due to wear in the axle bearing or wheel hub. Try this from both sides, but the problem is usually on the right side. If the wheel is rubbing the frame, I usually pull the offending wheel off and insert a 671M-19 thrust washer. The action of the worm on the worm wheel pulls the axle to one side or the other depending on the direction. The more load on the motor the harder it will pull the wheel into the frame. Should fix it now if you have this problem as it only will get worse.
