At the moment i can't get down to check the setup,as i have severe lumber back problem and laid up in bed unfortunatly, but would love to know what to do when i am mobile again.
All i know is that looking from the rear of this mower there is a gear and chain set up on the left hand side.

The operaters manual has diagrams which an expert like yourself wouldn't have a problem understanding, if you could possably have a look at this link which may answer your questions.
http://www.coxmowers.com.au/files/cox/pdf/2500%2025j1.pdf

Oh yeah, the vertical movement of the deck has remained the same as it was prior to the sqealing sound.

Thanks very much, what a terrific forum.