I agree the 6 blade fan is loud. I changed back to original 5 blade and still had loud. Finally, after changing both the clutch and different 5 blade fan, the noise is substantially abated.
Can you spin the fan with the motor off? The fan should rotate a couple of turns before stopping. If not, usually bad clutch (locked up). Did you try a known good clutch and fan blade? The one that came with my 64 looked OK. However it was not until I put on another that the noise went away.
I believe there was a 7 blade fan available. I have one, but have not tried it yet as my fan