What might be the problem with my losi mini desert buggy?

it was drivig fine and i hit ajump and when it landed it wouldnt go anywhere but the motor was still going and it was making a loud crackly noise from the dif area and so i took it apart and nothing appears to be wrong inside of it. if you go full throttle it makes the loud crackly noise and occasionally catches and goes but now it wont do it any more but when its in reverse it goes fine until something gets i the way or pressure opposite of it then it makes the crackly noise and goes no where.i took the pinion gear cover off where the motor gear and the bigger one connect and those are both turning fine, so should i get a new dif? or does it sound fixable. like i said nothing appears to be wrong it looks fine and there is no chipped gears