Trans: Gear oil or not ???

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Trans: Gear oil or not ???


Post by jbgoodner2 » Sat Jun 02, 2012 3:00 pm

I have been trying to learn why some say gear oil and some say regular oil . What is the difference? In an article in American Iron, Donny says use gear oil, the old manual says use same as in engine, several people on here (Trans Forum) say multi-grade !!! What's up ? Any input is greatly appreciated !!!! Ride Safe, and God Bless !!!!!!!!!!!!!

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Re: Trans: Gear oil or not ???


Post by 58flh » Sat Jun 02, 2012 3:16 pm

IF tranny is new multi-grade for break-in & change it out every 500miles, when you reach 1000-1200 FLUSH real good with the same wt. oil as motor 60wt. NO troubles,Also use a magdrainplug for peace of mind if anything else it cant hurt!---I rebuilt my own & have ALOT of miles on it now & shes in excellent shape! & that is how I broke it in! now its st.60wt same as motor!----RICHIE 8)

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Re: Trans: Gear oil or not ???


Post by 1962FLH » Sun Jun 03, 2012 2:30 pm

I know harley does not recomend this in the older bikes but they did not have multi grade oil to chose from back then however I use 20W50 in my 4 speed trany because using the gear lube causes ware on the high gear bushing. Gear lube is to thick to get between the bushing and the main shaft when new and tight causing execive ware and leaking. Eight years and 11,000 miles sence i rebuilt the trany and still no leaks. ps am also using a later style high gear with main shaft seal.

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Re: Trans: Gear oil or not ???


Post by RUBONE » Sun Jun 03, 2012 4:57 pm

Old original H-D trannys did not work well with gear oil (hypoid such as 80/90) for a couple of reasons. It did not lube the rollers well but primarily the high sulpher content attacked the bushings causing premature wear. Motor oil was and is recommended. Multigrade is fine, straight weight is fine. Just keep the level correct and change at regular intervals as they tend to collect moisture. If your oil is milky it needs changing!

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