I have the same issue, Its pretty loud, Kicks in after about 5 Seconds from first turning on the vehicle. Obviously, my AC hasnt ever worked since owning the truck.

I am wondering if running it with this gross noise is bad for it,
Anyway,
I believe I need to go through the same procedure as above if I wish to correct the noise.

How expensive is a new AC Unit? Or to have the clutch/pulley replaced on the existing one (if possible)?

 

Wow... This is an oldie... *Moving to 2nd Gen Tech*

Have you tried spraying some WD40 on the compressor clutch while it is off? What does this do to the noise?