If you look close you can see shims in this pic:
Its where you need to put diff shims to adjust gear mesh.
http://www.bigbigplanet.com/rccars/v2/v2_02.jpg
heres an article about it too.
RC411 :: Learn How To :: Shim A Diff
LSP lots of Khz, Werks .28 8 port.
Revo 2.5, TRX 3.3 Engine, Center Diff. Fast and Turns on a dime.