Its what their tech recommends. They have tested 75W90 extensively in Sportster trans. I have never had a problem. I take it you know more than Red Line. LOL

Here is Red Lines official response -

Thank you for contacting Red Line Oil, in the shared Sportster primary/transmission the 75W90 is recommended, a product that has been used extensively and performs well.

The 75W90 is the product we have have used for a number of years with very good results in Sportster/Buell transmissions, matching the viscosity and type fluid called for.
The 80W Motorcycle Gear Oil is a lower viscosity than called for, the ShockProof gear oils can due to their unique characteristics could cause sticking of the Harley clutches.
The 75W90 would be preferred and recommended over 80W Motorcycle Gear Oil in these applications.

There can be issues with some GL-5 gear oils in certain applications. Some can be corrosive to brass, bronze or copper, not an issue with our GL-5 gear oils, they don’t cause corrosion, pitting or metal removal. In a synchro equipped transmission the friction modifiers contained in many gear oils can make them too slippery, though not the case in a motorcycle transmission with dog rings.


So if you want the right viscosity and dont want to worry about it damaging anything, go with Redline http://www.redlineoil.com/product.aspx?pid=133&pcid=4

__________________

 

Its easy to find these things out...
Phillips 66, which was spun off from ConocoPhillips a few years ago. ConocoPhillips is now strictly an exploration company. Well - to be more specific, Red Line was bought by Spectrum, and then Phillips 66 bought Spectrum. curtesy of bobistheoilguy.com

http://investor.phillips66.com/inves...r/default.aspx


HD was getting their oil from Citgo. I haven't heard about any change. The SN3 bottles are not the same as Mobil 1 V twin bottles. At least not the ones in my garage.

According to the "Material Safety Data Sheet" for H-D's SYN3, it is chemically a blend of 60% synthetic and 40% petroleum oils.


(1) 1-Decene Homopolymer, hydrogenated
68037-01-4
50% - 70%

(2) Proprietary Ingredients
Proprietary Mixture
1% - 10%

(3) Polyisobutylene
9003-27-4
1% - 10%

(4) Distillates, Petroleum, Hydrotreated Heavy Paraffinic
64742-54-7
0% - 20%

(5) Distillates, Petroleum, Solvent-Refined Heavy Paraffinic
64741-88-4
0% - 20%

(6) Zinc Alkyldithiophosphate
68649-42-3
0% - 2%

Item (1) is a Group IV base oil. unable to locate the manufacturer of this base oil. Group IV and V base oils are the only "true" synthetics to the cognoscenti.

Item (2) is probably their additive package (boron, calcium, magnesium, phosphorous, moly), but it is conceivable there could also be some "secret" synthetic oil, maybe an ester type oil, included in it.

Item (3) is a fancy name for synthetic rubber (or elastomer) but this is probably considered to be "synthetic" oil as well.

Item (4) is a Group II base oil, namely Conoco Pure Performance Base Oil, either 110N, 225N or 600N. Pretty much no one is calling a Group II oil a synthetic.

Item (5), No specific information on this group but it is Conoco's Cit-Con 650N Base Oil. It's presumed that it is a Group I oil as it is solvent refined. Most quality blenders are not using Group I oils in their premium motor oils and they are not considered synthetics.

(From the MSDS for the HD 360 20w50 oil: The major base oil constituents in it are the same ones as are listed in Items (4) & (5) above.) H-D 360 is marketed as a non-synthetic, conventional (petroleum-based) lubricant.

Items (4) & (5) above, are likely needed to keep the old air-heads running without bearing skid and gasket leaks. This design flaw is clearly stated on Harley Davidson's own web site.

 

Are you sure about this particular point ? When I see the word "hydrogenated" it makes me think Grp. III. A Grp. IV base oil should be a PAO and a Grp. V would include Esters,, IIRC.

I'm not out to critique bro. These are just my personal recollections.

 

Don't know if Hydro cracked and hydrogenated are the same. I was cutting and pasting from Amsoils white papers.

 

This is what I have been using in past few years, Confirmed by Redline Rep

Red Line 57904 (75W90) Synthetic Gear Oil
Red Line 42504 20W-50 Motorcycle Oil

 

Yeah, me to. We got an internet expert who get his facts mixed up a bit. Sorry.

 

Everything I have read here and else where. I am going with the Red Line 57904. Many thanks to everyone who replied.

 

You will like it. I will never use any thing else.

 

BINGO, I use the same. I'm quite happy with the product. I will continue to use Redline products. Oil Threads, like talking about politics or religion in a bar.

 

Redline mt90 goes in my jeep tranny