At what mileage should you change the timing chain on a 2001 Dodge van 3500 59 liter engine?
A timing chain normally will last as long as the engine. Signs of a failing timing chain are chain noise and or engine that continues to jump time.
How many miles on 2002 jeep grand Cherokee limited can you go before you will need to change the timing chains?
The timing chain (not belt) is not a thing that you should have to replace on a mileage basis. Just keep the engine in tune, change the oil per manufacturers recommendations, and drive it. By the way, a timing belt should be changed approximately every 75K to 80K miles. Your engine will have a chain.
The Windstar engines are equipped with a timing chain. No scheduled replacement is necessary. Generally timing chains are only changed on very high-mileage motors if they are being rebuilt or refreshed. In most cases by the time the engine is due for a timing chain change, it could use a rebuild anyway. you should not have to do any maintenance to the timing chain because its internal and lubed by ''splash'' oiling though internal oil…
The manufacture lists the mileage at which the timing belt must be replaced. On vehicles that have an interference engine if the belt breaks you will have serious internal engine damage. The mileage at which it must be changed varies from 60,000 to 110,000 miles. As you did not list your make, model, year, or engine size I can give you no definitive answer. Look in your owners manual.