I'm puzzled, I changed the transmission fluid in my low mile S2k and after doing so I got input shaft bearing noise - it appears only when the clutch is engaged and disappears when the clutch is depressed. I only notice it in neutral, it's not loud enough to be noticed in this car when driving. ]

I used redline 75W80 GL-4 GEAR OIL as they recommend. Can it be the fluid? I've used redline before in other cars with great results. Not sure if I should swap to Honda MTF or try the recommended Motul, which is a touch thicker. I'm not sure what was in it before, I just know it wasn't the factory fill.

What's the best approach?

 

Changing to a different fluid won't fix a bad bearing. The bearing needs to be replaced.

I avoid Redline.