I can loudly hear the motor turning . It doesn't sound like it is humming. It appears to almost shake the engine in forward or reverse direction.  It was working fine just a few seconds prior to this . 

The NS covered wagon was purchased for Xmas 2013. It worked fine going in both directions.But now the engine will not move in any direction. The can be heard running inside engine body but wheels don't turn. Is there fixable soluntion on a hardly used engine?