When should I change the timing belt on a 2005 Toyota SR5 Tundra crew cab?

It depends. if you have the 4.0L engine,never because it don't have a belt,it is chain driven. if you have the 4.7L engine,then the recommended replacement is around 90,000 miles, under normal driving conditions; Water pump is driven by the timing belt. It is recommended that you consider changing the water pump and components when replacing the belt.