FLM does show diff cups for your E-Sav and they mention a full diff upgrade that uses the nitro Sav diffs, so there is help out there. I did not see much over at Sav Central either - I'm registered over there, but they can be pretty snooty so I don't spend much time there anymore.

It would be nice to find some info on what others are doing about the probs you're having. Check some of the big boards out too like Radio Control Zone and RC Universe.

I'm always amazed at what I can find using a search engine!!