I am going to be replacing and wire the ring gear bolts. Have been told that after market equivalent strength bolts with lock washers are superior to the oem type having the serated flange head. It was suggested that this serated flange design,as the locking mechanism was the primary cause for bolts to become loose. Closure on this matter will be greatly appreciated.
Original Post
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.
Thank you Jack for timely response. So I gather you agree that the oem pricey bolts are not superior/necessary? Although I went into the shop this eve. and took a very good look, with magnification, to inspect the areas where the stock serated flange bolts made contact with the mounting ring portion of the differential carrier. The bolts definitely scribed marks which did catch my finger nail into the surface, fairly uniformly with all 10 bolts. Would inside or outside tooth star washers be better than split loc washers?
Thanks again
Vince
Stock ring gear bolts are hardened to approximately US grade-8 and seem to be hardened all the way through, which makes them brittle. US-made replacements are not over-hardened and are much tougher, which works better for shock-loads like when 300 horses are routed through a differential. The serrations under stock boltheads work, or don't work, as Marlin mentioned. US bolt mfgs provide a washer so there's a compatible surface under the bolt head. I don't suggest mix 'n matching high-stress parts such as this. Star washers are mostly to combat high-frequency vibrations, which is not what we encouinter here. Stick with whats in the provided kits. I advocate torquing to ZF's spec and using US made bolts with aircraft-grade 032-thick stainless steel safety wire.
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