2010 Ultra Classic, pulled out the Syn3 at 400 miles. When I pulled the drain plug for the transmission and saw the metal fuzz on the magnet, I decided that the Syn3 was not going back in their. Granted it was a new bike, and some of it could of been from things breaking in, but, If that was from only 400 miles I wasnt waiting till 1000 to change it. I couldnt get any Redline Shockproof, at the time so I ran the Amsoil 74/140

 

Amsoil 75-110 SeverGear for me. I tried the 90 and the 140 really could not tell much difference but is was much better shifting than the 20-50

 

I'll toss in my 2 cents on gear oil.
I'm running a '07 Ultra Calssic, just over 15,000 miles.
When I got it (used) I dumped all my fluids and on the advice of my dealer (parts guy), added Screamin' Eagle oil to the tranny.
HOLY SHEET!!! I thought I blew it up, gear chatter up the ****, (I came off a Kawi Vulcan, so I knew sheet about the newer Harleys).
The service manager said to run "Red Line gear oil"
It was red and kinda like jello half cured.
Did a PERFECT J.O.B., no chatter, shifter easy.
I had switched to Amsoil motor oil before I went to Daytona, talked to the rep at Daytona and figured I try the sever gear oil. (I was tired of 4 different oils for all my bikes and such, I wanted 1 brand of oil, figured Amsoil was working well in the Harley, if it was good in there, it should work in everything else)
When I got to 15,000 I put that in.
Yesterday I went on a fast 150 mile ride, (took the bike to look at a jeep project) on the interstate.
When I got off the highway back home, there was a TINY bit of gear chatter.
I never had that with the Red Line oil.
I'm gonna run it somemore, but if I hear the noise, I'm dumpin' the Amsoil and going back to Red Line.
Joe
I ride,therefore I am.

 

I have Wal mart 75W140 syn gear oil in mine now after 20W50 and Amsoil severe gear and i can honestly say i can't see any difference at all...47000 miles on the bike.

 

I've run about everything in mine , AMSOIL , Lucas and I now have Redline in it and I honestly can't tell little to no difference in none of them! If I where to give a edge to anyone it would be the Lucas!

 

I run it, shifts a lot smoother.

 

The 75-90 Wt Severe Gear Oil is a great oil. Keep in mind 5th gear sings a little because it's supposed to. The heavier oils do nothing to quiet the gear noise it just insulates and reduces noise. Bearing makers want the thinnest oil possible to run the bearings in. They will run cooler and last longer. It also is good for fuel mileage.

 

You are right in one respect. Engines have closer tolerances now and can run thinner oils, but gears are different. They need heavier gear oil to help during backlash. That's where Redline with shockproof is better I think. I also believe Amsoil and others are great oils. If I were using Amsoil or Mobil1. I would use the 75W140 I believe in the long run it will protect your transmission gears better.

 

put 45000 pn my rk 07 ran amsoil svg 90/110 in tranny and 20/50 in primary and engine all was well. runnin the same in my 2010 limited and it is workin fine

 

As long as you keep the beeeatch greased up you doing ok...