I am sorry that the assembly did not go as smoothly as it should.
I would not recommend to put shims in the assembly since the slop in the gears is compensated naturally while the gears are rotating.
I am using this axle housing both front and rear for about two years now and never had problems and I abuse my jeep a lot.
I hope you will be able to enjoy your axle housing eventually.
You can find pictures and information on a forum thread I posted:
To complete the build you will need:
1. the internals of the cc01 axle.
2. cc01/ta03 axle.
3. 2X tamiya 54490
4. Hex Socket Grub Screw - M3 x 8mm or similar.
This is a replacement to the independent suspention.
Custom work will be needed to be done so it can fit.