If you have the new metal diff for the brushless Evader, you best open it an check it out, it's probably dry, or near so. My bevel gears have worn out after only a month or two. DTX suggests using TrackPower gear grease instead of fluid, as, even the heaviest fluids tended to leak out. (!!) It's probably also a good idea to use thread-lock on all the diff screws.

Update: Thread-lock is a MUST. And the only way to get it to work is to disassemble the diff, clean it all out with solvent (especially the screw holes), let it dry and use the thread lock on one side and assemble that side. Load it with grease, carefully avoiding getting it in the screw holes. Then apply thread lock and assemble the other side. Let it sit for a day or two. This should keep the dang screws from loosening and destroying the inner diff gears. ALSO, get yourself some 1.19mm "music wire" for the drive-cup retainers, the originals are not strong enough and will eventually fail. You should be able to find it at your LHS.