Read all instructions first please.
First, seeing an exploded view will help you, so click here..
Then click on the button labeled 42590A XXXXX.
Look this over...
1. Remove mowerdeck
2. Diagram current belt path around each pully, idlers, and belt guards (esp position of belt guard).
3. Depending on exact unit you will either loosen the belt guards around the rear transmission pully, or if there are not belt guards there, the Frame is being used as a belt guard.
IF this is the case, you MAY have to loosen the bolts holding the transission ON ONE SIDE just enough to allow you to slip belt through the gap. (you may have to drop the transmission several inches without damaging the linkage).
There are also belt guards on the double stacked pully on the engine that have to be loosened as well.
must remove from rear pully FIRST..
Reverse prosses to install new belt.
Double check exact location and placement of belt guards, idler pulleys and drive pullys from you diagram.
Nothing can rub anything..
NOW, We must KNOW why the belt needs replaced in the first place.
Something caused it to go bad.
Could be a bad Idler pulley, a bent idler arm, bad allignment of the pulleys, obstruction, etc..
If you do not determine the CAUSE of the problem to the belt, It is Going to happen again..
Inspect and examine everything while you are down there.