I've been using V-twin 20-10 for 40,000 miles in all 3 holes, no issues.

 

I run M1vtwin in the trans...I put in gear oil once and I didn't like the way it shifted..it felt kind of sluggish going from gear to gear (but it was quieter on the high way)...I figure it is partly because it only had 4000 miles on it when I put in the gear oil, and as it gets more miles on it I may go back to gear oil...

 

damum that is pretty thin stuff lol.

 

You are the first one that makes any sense, But, If some of you guys like to hear that 5th gear whine,well that is up to you

 

I think they fixed that in newer bikes. My 2011 does not whine in any gear lol.

 

yes they fixed it,they went to a weeker sphryical cut gear vs the stronger streight cut gear.spectro gear lube in the gear box (although any good gearlube is fine with me) motor oil in the motor(dont want v-twinn in my motor).primary gets v-twinn(lack of friction modifiers make it safe for clutch but bad for motor).

 

[QUOTE=OU812;8688756]You are the first one that makes any sense, But, If some of you guys like to hear that 5th gear whine,well that is up to you[/QUOTE

Never have had whine or any other noises in my 07. Lucky I guess.
75-90 and IDS.

 

You can use anything you like in the gear box, but why would you not use a 'gear lube' instead of a motor oil?? Cost is about the same. Gear lubes are made for...gears. 75-90 synthetic would work fine. Viscosity is rated different for gear lubes.

 

but harley says........... they used to say synthetic was evil ,till they started selling it!

 

I've been in the heavy duty truck parts business for 31 years. About 25 years ago Eaton started specifying straight 50 wt oil for their transmissions. These trucks are driven by everything from good, experienced drivers, to some of the worst cowboys you ever saw. Lots of them go over a million miles, pulling 80,000 lbs. These 13, 15 and 18 speed transmissions have way more moving parts than a motorcycle transmission.

I know a few old men who won't use what Eaton recommends, because their grandpappy told them they had to use a heavier weight oil in a gearbox. They think they know more about it than the engineers who have done extensive testing and determined that 50 wt. is the ideal oil to use. I don't think they do.