I need a diagram on how to replace a belt on the Sears Craftsman II 4000 riding mower

You have three belts, which one(s) are you trying to replace? If you go to sears.com (http://www.Sears.com) and get into the lawn and garden section you can download the owners manual for you tractor. Lower your deck all the way to replace belts. Pushing in the clutch/brake will give you room to remove the drive belt. Disengaging the blade and pulling back on the tension pulley will give you room to replace that belt.

Sometimes the diagrahm is on the deck for blades and under the foot rest for drive.

I need a diagram on how to replace a belt on the Sears Craftsman II 4000 riding mower
Might try looking under the foot rests, I have a older craftsman that has a belt diagram under the left rest.

I was having a hard time finding a manual for my mower. This helped immensely!

You can also look at dixiesales.com and find diagrams and parts list for craftsman and many others.

Riding mower manual

You can go to dixiesales.com and get your manuals part number and order it from sears.com

How to replace 46inch cutting deck belt

I need a diagram to replace the belt on a Craftsman riding lawn mower