yep - lithium grease etc - it doesnt have to be exotic stuff, just something nice and sticky to keep some on the gears at *$%!! rpm...

i filled the holes in my diffs and filled em up with general purpose grease that i use on the 1:1 cars wheel bearings!! dunno how it handles yet.... it has stiffened the diffs up a fair bit tho!.....and added a ton of weight to the drivetrain.