RE: exceed 1/8 mad torque is running in front wheeldrive only ?
try turning 1 rear tires while holding the other. if you can, then the axle will need to be opened up as the diff locking part is missing or broken. both wheel should turn together as the diff is locked.
if they do both turn together, then i would open up the motor cover. see if the pinion is meshed with the spur, or if the pinion is loose on the motor's shaft.