You should search this thread for you questions before posting a new thread:
http://www.rctech.net/forum/electric...10-thread.html
Regarding your query, first make sure your slipper clutch can slip--just a little--during normal driving. Otherwise can you tell us what circumstances they broke in and what condition your bearings and differential outdrives are in?
At the very least, if the parts are very new, you might be able to warranty them through Associated. Give them a call.