I have a troy bilt model 609 and the mower will not engage

Does it have a electric pto or manual.
Did you check the belt make sure it has proper tension

Troy bilt 42" rider. Will not come out of gear( forward or reverse) Trans Model # 618-0307. The shifter shaft does move in and out with no changing of gear position. Is there a common cause for this problem and what's the fix?