Repairs Hard to explain

Have craftsman 24HP automatic lawn tractor. This problem just started. When depressing the brake, clutch pedal (Left foot pedal), and releasing when released to almost top position (towards seat), drive belt makes chattering noise. Not in mower deck does this without deck on. If barley resting left foot on pedal or placed 1" block of wood between pedal and foot rest noise stops. Tractor moves fine in forward and reverse. Not drive belt brand new, and all pulleys seem ok. Seems like pedal is traveling too far up or towards foot rest. Cannot find any adjustment. This rod goes to belt pully to put hydrostatic in and out of gear. Forward and reverse are on other side. Rod also goes to transmission lever with spring. If I pull back on pedal towards operator makes chattering noise worst. Any thoughts on this problem? Sorry to be so vague. Will supply additional info. E-mail is mudmixer@yahoo.com. Thank You