I’ve never checked the tech specs on sizes and tolerances before building a kit, so of course I never checked mine. All I can recommend is that you build the kit according to the directions, and hope it works out. Xray is renowned around my area, for having absolutely exceptional customer service and support. There was an issue with one of the local racers XB8TQ kit, that the center diffs gears were part of a batch that missed a hardening process, and they stripped relatively easily after only a few races.
He contacted the local Xray representative, and was shipped a new set of gears immediately. I can only imagine that if you have problems with the diffs, that any local Xray rep will help out with the same exceptional service we have become accustomed to.
It's just my opinion that I want to build my kit fast as I can, and get playing with it
You on the other hand may want to talk to someone about the differential gears and maybe have a new set shipped to you.
Cheers