The early 1/12th cars I ran were straight axle, no diff at all. At some point, I ran the delta gear diff (a long time ago, in a place far far away...) and the thing I remembered most was the tendency to strip the teeth on the spur any time you had an abrupt stop, like hitting something. Now I know we are trying to not have that happen, but it does. The material may have been too brittle that they molded the spurs out of, but it may just be an inherent issue with gear diffs in 1/12 or 1/10 pan cars. Since a ball diff will give a little, no matter how well built to not slip, it does help alleviate this problem. I would guess that the TC cars do not develop the grip with the narrow rubber that the wide foams do, and the amount of give in the belt drive system that most run is why they have not seen many similar failures while the gears diffs are in vogue in TC right now.

I still have a few of those Delta gear diffs somewhere. I should dig them out...

-a