wheel bolts

I haven't had to take wheels off my BX2230 very often, but when I did, I always cursed the damn wheel bolts. They are a real PIA to get back on, even after I made a couple of alignment studs. A while back, I replaced the front wheel bolts with 7/16"-20 studs and nuts, and the one time I have had...

Anyone have any suggestions as to what may be causing the lug nuts in the front wheels of my John Deere 855 to loosen up? I did the 500 hour service about 4 years ago, about 1 year before the problem started. When I changed the transaxle oil I was not aware of the breather plug on top of each...