I had that problem on my wheel drive shafts. Turned out I was using the drive shaft yolks from a Maxx 3.3. They are a little different from the Revo yolks. This post from an old thread of mine should explain better what I'm talking about.
http://www.rc-monster.com/forum/show...6&postcount=48
I'm not sure if this is your problem but it sounds similar to the problem I had.
Hope this helps.