Small Engines (Lawn Mowers, etc.): john deer rx75 mower deck noise, noise question, belt tension

Question
how do I adjust the belt tension for the blades or can this
even be done?

Answer
http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.H...

Looking at the diagram at the link above, I do not see any adjustable
linkages.  But reading your title makes me worry.

What kind of noise? a dull roaring noise?  The belt seems loose and you have noise?

I would suggest you remove the belt, and then spin the blades and all of the pulleys by hand and look for bad bearings, you will know
when you spin the part.

If not, let me know what you meant by the deck noise question, and
some more detail, but I wouldn't mow with it like that, it will just get more expensive, and possibly dangerous.

Let me know,

   Fish