I'm currently running Syn3 in all three holes of my 2004 RK FLHRI. I saw a bunch of Facebook posts in a group thread of guys saying they run gear oil in their transmission. Some were running 75W-90 and some 75W-140.

Is that too thick of an oil for the trans on a Harley? What are you running in yours?

 

I run 75/140

 

I have run Formula+ , Redline Heavy Gear Oil with Shock Proof, and I am currently running Amsoil 75-110 Severe Gear. Can't tell the difference between any of them. Next time I will run Lucas Gear oil 75-90 just for fun.

 

Only people who like there transmission use gear oil.

 

Red Line Shockproof here also. Not sure on weight, but man its some thick sheet.

 

I use gear oil in my Panhead ( ball bearings in cages)

My evo and my twincam use HD Primary +

why? they were designed for it , the bearings, the gears, the shear resistance and the gaskets.

I tried redline once- no improvement to the straight cut gear whine

a "thicker" oil will fill some gaps, but may not flow as well into tiny crevices, it will provide resistance ( which makes heat)

Mike

 

Valvoline 75W-140 Full Syn. here. Went from Redline Shockproof to this. I like this better.

 

Getting ready to change the oil in mine. Dealer did the changes when I bought it last July with 10k on the clock, not sure what they used other than Dino in motor. But I'm going to add SuperTech full synthetic 75w-140 gear oil as I'm a firm believer in "if it has gears, use gear oil"!

In fact I'm changing all 3 fluids to synthetic. Hoping for a less "clunky" shift, but if not it will still have fresh fluids...

 

got my tranny apart right now (2006 5 spd) replacing 5th gear; going back together with Amsoil Severe Gear 75W-110 (synthetic)

 

I'm using the Spectra 6 speed synthetic transmission oil and my dad is using the belray 75-140 synthetic gear oil. Both run very well with no issues. Both bikes are 2015 SGS's.