[Dick Linn]

Lacking a more complete description of the symptoms, I would check the alignment of all mounting holes and components on that side. Make sure that you have the motor and drill gearbox are mated, seated and aligned properly. The motor and gearbox shafts should be absolutely parallel, in the same plane. If they are mounted on the same flat plate or surface, one side should be good, but you may not have the shafts parallel in the other. Remove the motor mount bolts, grab the drill transmission clutch collar (with the numbers) on both sides evenly, pull it snug toward the big gearbox shaft and see if the mounting holes for the motor mount bracket still line up. I put my thumbs on the big gearbox, fingers on the drill gearbox and just squeezed evenly on both sides toward the big gearbox. (We did this before marking and drilling any holes and also before tightened anything.)

Verify that the motor shaft in the big plastic helical gearbox is securely retained on both ends, with no end play. It should not move end-to-end. Also run the drill motor with just the one aluminum hex adapter screwed on (no plastic shaft coupler) and see if it runs true or wobbles. We have one motor that wobbles and one that runs fine, and I have heard others mention this. (We have a replacement aluminum hex adapter coming tomorrow.)

I also noticed that the hexagonal aluminum adapters were a very snug fit in the black plastic coupler and didn't readily fit all the way in due to the tolerances of the molded plastic. As they ran, they would drift back and forth when driving from forward to reverse if they were not properly seated. I gently tapped them in (using a soft-faced hammer or wooden block) until they completely bottomed out on the web in the center of the black plastic adapter. After inserting and removing the sharp-ended aluminum hex pieces several times, which sort of machined out the imperfections, I then beveled the sharp edges of the aluminum (inside the adapter part) so that they can be inserted and removed relatively easily (not sloppy!). I figured that this would reduce misalignment and stress and allow it to be more easlly butted up squarely against the big gearbox. That takes care of axial misalignment.

We did a lot of minor part fitting and smoothing to get the shafts, keystock, adapters and all carefully assembled and everything pressing nicely and squarely against a shaft collar that is riding on the inner race of the big gearbox bearing. I hope the plastic hex shaft adapter thing serves the purpose of absorbing a bit of shock and minor misalignment...

Hope this helps you. You can find the problem and fix it! Let me know how it goes.