I still go back to the fact that Mbil's own site says NOT TO USE there GL-5 gear oil in the Harley transmission, that is all I need to know. I mean, if the manufacturer trying to sell as much of his oil as possible says NO, come on.

Concerning the Redline - yes Redline has GL-5 rated oils. But nowhere on their site or anyplace else I could find does it say that their motorcycle Trans Gear oil is GL-5 rated.

 

Why try to cheap it?
Stick to the Mobil 1 V-Twin 20w50 Syn all 3 holes and ride.

 

Dealer here sells Redline Shockproof as well as aftermarket shops. I've been using it for 40k miles, it really makes the trans smooth and finding neutral easy. I don't think you have to worry about corrosion in the trans.

 

I wouldn't recommend running any motor oil in the tranny, only gear lube. Also, anything more than a good quality dino oil in the primary is a waste. It isn't recommended or needed.

 

ditto.....

 

GL 5 oils damage brass bronze and copper none of which are in the six speed, been running 75w140 for 5 years no problem

 

There's no need to pioneer new frontiers in this area. All respectable manufacuters of oil provide clear information. The mobil 1 warnings about using Gl-5 in soft metal trannies was already brought up. In the attached, a different manufacture shows for harley twin cam 20W50 motor oil in all holes and offers two alternative gear oils for the tranny, both alternatives are GL-4 rated and not GL-5 rated. This manufacture does sell GL-5 gear oil, but in the attached chart only list as an alternative to motor oil two products that are GL-4.

 

Thats all good and well but, that publication is written by Amzoil and just like The Motor Oil Bible its slanted towards its own products.

 

Yup.. I think this is the key. No soft metals in the H-D 6 speed tranny. I just read my owners manual, and while it does specify to use Formula+, it doesn't say not to use a GL5 lubricant. I think they'd be pretty quick to point that out?

 

i had heard of this gl5 warning before and began doing a bunch of research. i found out 2 things, first being no bronze or copper in the hd transmission to worry about, and the second being that even though gl5 is corrosive to yellow metals, the manufacturers put some anti corrosive agents in the oil. they will eventually break down, but, not in the 20k mileage change interval that hd recommends.