I block sanded the backside of my left aluminum hub with 600 grit. Then had to carefully deburr it and doing so will keep it from bottoming out on the e-clip. The plastic and aluminum hubs are quite different and it appears the Atomic diff was designed around the stock plastic part.

Still would like to know how you got it to work so well. The gear teeth are a different pitch and/or profile from what I have seen.

After a close look at the Atomic diff I figure that someone along the line screwed up and released it with a bushing width 2mm wide ball bearing instead of the 2.5mm that it needs, a 0.5mm spacer/washer between the 2mm bearing and thrust washer housing would also work. Note that with a new 2.5mm bearing it now matches the Kyosho Ball diff’s spacing exactly.

http://lbspd.com/v-web/gallery/album...ompair_400.jpg

Another problem I had with the Atomic diff is that the adjustment nut tended to loosen up as you drive, but a drop of thread-lock fixed that. I use the non-hardening type and put a small hole in the motor mount so the diff can be adjusted by holding the nut with a push pin or small screwdriver while turning the left wheel.

http://lbspd.com/v-web/gallery/album...iff_Adjust.jpg

Even after replacing the bearing I can’t say I’m exactly happy with the Atomic diff, the gear pitch seems ok but there is definitely something wrong with to shape of the teeth, too wide, so it needs to be backed off from the pinion more than I like and even then you can hear it so even if it's not affecting performance it's still annoying. However the lap timer doesn’t lie so with the new bearing, lock-tight, and mount access hole I guess I prefer the Atomic over the Kyosho, but only marginally. With work both can be worth while but it took forever fiddling around with spacers and eventually new springs for the Kyosho’s average lap time to actually improve on the stock gear diff, with the right size bearing in the spare parts drawer it only took a few hours to dial in the Atomic. Note, the Kyosho ball diff in the above photo is out of an 80 gram modified Epoch not a 45 gram dNaNo so even though the spring on it is lighter than the stock spring its still heavier than the one I ended up using on the Kyosho ball diff in my 962C Porsche.

I started liking my Kyosho ball diff. I have it set at the maximum loose setting without slipping. I had to grind the top and bottom plastic pieces on a sand paper to lessen the spring force. Do you guys let it slip at all?