I have a Murry 14.5 hp 42 in. cut mower. The model number is 40508X92. I need a daigram for replacing the trasnmisson belt. The area I am having a prblem with is at the tension pulley.

Hi,
Bit of a puzzle since you say 42" and the model number says 40" (they look alike.) At any rate your parts breakdown is here:
http://www.outdoordistributors.com/pdf/Murray/MURRAY-MODEL-40508X92A-LAWN-TRACTOR-(2000)-PARTS-LIST.pdf
Peace,
Clarke