can u give me a diagram on how to replace belt and pulley for a whrilpool model AP2911909
The model number you list is for the pulley.
Please list the actual model.
If the problem is just how to loop the belt here are some diagrams.
http://forum.appliancepartspros.com/dryer-repair/25860-dryer-belt-diagrams.html
Also the following may help
341241
There are other videos on YouTube for different models.