GA- great assembly =
http://greatassemblyrc.com/ They sell 6061 & 7075 alloy bulks which are very strong, but a little pricey.
The grey bulks are the newer improved version on the t-maxx3.3, but they should work on an emaxx fine- slightly stronger, and the grey skids too.
The flm combo bulks come in two flavours:
FLM17500
FLM18500
$120.00/set = these take standard maxx diffs (minus the casing).
FLM17700
FLM18700
$140.00/set = these take 1/8 buggy diffs which mike sells, but they will require more work to set them up (shimming and gear alignment etc)
If you are on a budget like me, I'd go for the FLM alloy bulks:-
FLM18001 $37.50
FLM17001 $37.50
They looks lush and are still a great improvement over the stock plastic version. As for checking your diffs, you may have to dismantle them if you cant feel/ hear anything obviously wrong with them