first off dont get discouraged. wrenching is just as much a part of this hobby as running is.
what did you do before to "fix" it?
the slipper we mentioned is a large plastic gear, that is held agains a metal plate by a tension spring. if this spring is not tight the gear will just slip (its a slipper) on the plate. this is designed to be a weak point on the drive line. on a hard landing, or something this slipper will slip and not transfer that torque to the driveline. if it is loose it will slip to easily and not allow the truck to move forward.
start the truck, put your foot, or something solid in front of it. slowly apply throttle (not to much better in blips) and watch the driveline. look at the clutchbell, is it spinning? if so, is it turning the spur (large plastic gear) if so, is the shaft the spur is mounted to spinning as well? if yes, look at the driveshafts (run lengthwise on the bottom of the truck) are they turning? if yes look at the outdrives (from the diffs to the wheels) are they spinning? is any one wheel not spinning but the others are?
it sounds to me your slipper is slipping to much and you burnt up the friction pegs. It could also be a trans issue, or the diff. but if its a diff, only the front or the back wheels will spin and not the others. as roles stated, it could also be to tight of mesh at the spur and the clutch is slipping.
