Timing chain or belt on 3.5 motor & recommended replacement?

it has 3 chains! there is no required service on the chains,like there is on earlier models that had a timing belt. the chains should last the life of the engine,just keep the oil changed on regular intervals.i can say that i do have an ole 2000 F150 that i drive every day and it has chains..it is the original engine,never rebuilt,same chains from the factory,and i have 324,000 miles on it now.there is one thing you need to watch out for though..you can read about it by clicking on Problems to the right of this page towards the top..when you see this,click on it and read>>>"Massive Oil Leak and Loss of Oil Pressure on Toyota Sienna"...it is not a recall!