I just bought 6 quarts of Amsoil 20w50 for my RKC and it says to use in all 3 holes. A lot of people are recommending 75w90 severe gear for the tranny. Will I be ok with the 20w50 or should I switch and why? Thanks

 

Save the 20w50 and get some amsoil 75w90 or 75w110 severe gear for your trans. Don't worry that 20w50 won't go bad on the shelf. A motor oil in a trans will shear out of grade faster then a gear oil. Plus gear oil will give you better & smoother shifting and quieter operation. I would get the 75w110 myself if you like amsoil.

 

Thanks for the advice. Why the 110 over the 90. Any specific reason

 

Thicker when hot.
Ron

 

No to same stuff in all holes amsoil or not
http://www.hdtalking.com/look around oils and lube do your home work

 

When it gets hot it has more viscosity improvers to thicken it to a 110w vs a 90w. I use the Redline Shockproof Heavy (75w250) and it quiets trans noise and gives you better protection at higher heat ranges. The 75w110 will give you great performance.

 

If you can not get Spectro GL5 for the 6 speed the REDLINE is the one I use because spectro to hard to get Moto oil does not belong in gear box

 

I'd use the 20W50. Look on the bottle, it meets GL1 specs, which is all that trans needs. Extreme pressure additives are only necessary in hypoid gear setups, and there's no advantage in using them in a transmission.

 

cause it shifts soooo smooooth. I might go back to 20/50 just to get that classic Harley CLUNK.

 

Just did 5k oil change and did tranny too. Used Royal Purple 75w-140. A little quiter, not much. Still got a "clunk". No more whining, though. Next change I'll switch over to Redline shockproof.