Repairs craftsman zts7500 jerking

[mustang]

help... zero turn mower is jerking both right and left. replace the drive belt but no help. checked shock absorber and seem to be ok. cant believe both drive boxes would go bad at same time. anybody have any idea what problem is???

 

[mechanic mark]

Manual Craftsman Zero-turn rear engine rider 10727790 | SearsPartsDirect download second manual at bottom left of screen page 34, mower steers or handles poorly, check tires for proper inflation.