problem: my dad's mower which is a yard machine 2006 vintage will not move..starts right up but put it in gear, nothing...tries to move a little then nothing....so far i found the front pulley which is a double type of pulley bad ...so i replaced the front pulley and the drive belt , still won't move...seems as if the rear pulleys are turning but the mower won't move...any idea? i am getting frustrated with this machine as i dont have alot of free time to mess around with it..is there anything that is known to go bad on these machines that i should look for? i tend to think he has some trans problems but he won't buy that..thanks for any help