I have a jd z390a mower and had to drop the left transaxle to replace the leaking rubber plug located under the drive pully. upon reassembly of this pully back on the spindle I noticed that the spindle had an empty notch on same and need to know if there was a key inserted in it that may of popped out unnoticed when I took the pully off or does just the nut and washer on top of fan somehow keep the pully from slipping when tightened?????? want to make sure before putting back transaxle so I didnt have to pull it out again. please help!!!