Tried most of all gear lubes Amsoil,Belray,HD stuff, I'll stick with Redline shockproof seems to work the best in my bike & don't mind the smell.

 

The OP asked about viscosity. Engine oil and gear oil viscosity NUMBERS are different in an attempt to prevent gear oil being put into engines (some gear oil additives can be harmful to engine parts.) As far as viscosity goes, 20-50 engine oil and 75-140 gear oil are about the same. Since the factory still says 20-50 engine oil in the transmission, then 75-140 gear oil is certainly suitable for the transmission from a viscosity standpoint.

There are very few applications specifying single weight oil anymore. By its nature, a single weight oil will be: 1. Too thick when cold, 2. Too thin when hot, 3. Only just right at some point during warmup, still too thick cold and too thin hot. Modern petroleum engineering has provided excellent multi-viscosity choices for both engines and gear oil uses. The consensus is engine oil for the engine, gear oil for the transmission.

People closer to Red Line products than I am have stated that Red Line V-Twin with Shockproof is identical (except for the container) to Red Line 75-140 with Shockproof gear oil. If you choose Red Line products, buy which ever one is in stock or less expensive on the day you buy.

Your straight 80 weight gear oil will do the job for you but when cold will cost a little fuel economy and will require a bit higher shifting effort until warmed up. If it were my machine, I would get rid of the 80 weight stuff before next summer when the 80 weight will thin out a bit more than the 140 side of a multi viscosity gear lube.

 

http://www.redlineoil.com/news_article.aspx?id=49 Redline is calling their V-Twin Trans as a 90wt. SAE Gear oil Viscosity classification for 140 is off the chart for any crankcase oil. 75-90 would be as close as you can get to 20-50 crankcase oil. Looking at my Comparative Viscosity Classifications chart, the V-twin Trans with ShockProof is about equal to 40-60 engine oil, may not be the best choice for the really cold weather riders, but for most of us, is just fine and what I run in my bike.

 

I'm running Red Line V twin shockproof. It works well. I am also using their product in the primary and engine. Good Stuff.

 

same fluid in all 3 holes has to be a compromise somewhere. 3 different lubrication needs. no single fluid can be best in all 3 situations.

I swear by the redline heavy duty with shockproof. smooth as butter and quiet.

 

My vote is Mobil 1 75/90. Have it an 85 Evo, had it in a 96 Evo, 02 Twinkie, 08 Twinkie and present 09 TriGlide. Recently had reverse gear installed in 09 and Indy swears by Bel Ray products. Spring will part with BelRay and install Mobil 1. Never a problem with Mobil 1 products.

 

^^ I run the same. Quiet and nice shifts.

 

Google. Bert baker trans oil article

 

Agreed! JR

 

+1 Tried them all, I like Redline Shockproof. SJ Ron