If the brake is on or you're holding the spur gear while you turn one wheel, the other should turn the opposite direction. If you're doing that and they're turning the same direction.. I don't know, sounds like the diff is completely screwed up.

How you set the slipper depends on how you're running. If you're going to be bashing and running off road, you'll want it more loose to help prevent wheel spin and to absorb the shock of landing jumps and etc.

You can go to the "manuals" section of www.rc10.com and order a manual for $3-4... I highly recommend doing so.