Here's the way I see it: The serrations Do NOT work because in order to "lock" the bolt, the serrations must "cut" into the Metal of the Ring Gear, which is HARDENED, so they can't, and therefore don't!! In order for a "split", "locking" Washer to work; as it tries to backout, the sharp edge of the "split" cuts into the metal of the Ring Gear, which...Same as above! "Safety Wiring" is the only sure way. That's why it is used on Most Every fastener on an aircraft, which suffers from very high frequences that will loosen even the tightest of tourqed fittings. And where Safety wiring is not used, Nyloc Nuts, and 12 point nuts with Lock-Tight, are. EVERY fastener on an aircraft has a "safty", even turnbuckles! And doing those is a science just by themselves. Lastly; I have notice some safety wiring that is performed improperly. When finished, the wire must be absolutely tight! Tight enough to "sing" when plucked like a guitar. The wire must pull the bolts CLOCKWISE, (except in the case of lefthand threads). One bolt tries to come loose and tightens the second; the second tries, and tightens the first, ect! No more than 3 bolts may be safetied with a single wire. I know of which I preach. I graduated from the U.S. Army School of Aircraft Maintainance and Repairs, Fort Eustis, VA. in 1970. You had to know it perfectly. We could "Wire" in places so tight that you could not even get your fingers in there. The solution? You used two Needle-Nose pliers, one in each hand, to twist the wire! We were Experts! Regards, Marlin.