About a year ago, I changed over to Drag primary fluid. Ran it for a while and noticed extra noise coming from the primary, so I went back to Formula+
About 2 weeks ago, I changed my Derby cover, so while I had it off, I figured I might as well do the fluid. The only fluid I had in my garage was the Drag.
After running it for 2 weeks, I couldn't take the noise any more. Just switched back to Formula+ and she's nice and quiet, or as quiet as a Harley can be.
Anyone else experience this?
I run Amsoil in the crankcase and Severe Gear in the tranny, but the Formula+ seems to work best in the Primary.

 

Yeah it depends on the viscosity of the fluid. I tried using ATF in there for a little while and OMG it was ridiculous...so I went back to what I'm using now. I can hear it spinning at freeway speeds but there's a big honken chain in there so its not going to be quiet. I just make sure its wet clutch compatible and has more consistency than tranny fluid. What am I using....Rotella T6 same stuff they use in big rig diesels.

 

I have only used RedLine fluids.
I find them all excellent. The primary fluid allows for positive engagement of the clutch and releases fully without creep. No excessive noise.