The trouble is the final drive doesn't keep purchase with the gearboxes. The gears chatter and click. Upon dissassembly i find the plastic final drive cover that was modified with bearings has cracked on the inside and the shaft climbs and skips off the gears. My solution (with a hint from Jeff O) was to make the final drive a solid piece that prevents shaft wobbling. Fortunately I have some spares from a junker Merit T34 (thanks Aimee) I used epoxy to fill the voids. When it dries I will let you know how it went!!!

IMG_0074 by Ethan Dunsford, on Flickr
IMG_0075 by Ethan Dunsford, on Flickr
IMG_0076 by Ethan Dunsford, on Flickr