Z421 Z turn making a noise

[Butch]

My neighbor has a new (<50 hours) Z421 that has developed a noise. If you poke your head low behind the seat over the transaxle on the starboard side of the mower you can pick up on a grinding knock sound. You can hear it really plainly when the blades are not engaged. I can't tell if it is from the tranny or the motor. FYI... He changed the motor oil in the tractor the week prior to developing the noise. Any thoughts?

 

[lugbolt]

tell ya neighbor to look for some junk stuck in any of the pulleys. I see it all the time, pine cones, leaves, sticks, rocks, and especially sweet gum balls, stuck in the pulley and they cause the belt to "jump", and thus a knock, vibration, etc.

while they're looking at the pulleys make sure the hst pulley fans are intact. Not too much of a problem usually unless the belt's been throwed off at some point, then it usually knocks the hst fan off or just breaks a blade or two, which causes noise/vibration/etc