Belt. That engine is based on the 3.5L v6, so it shares the same belt
arrangement. The good news is that the 3.5 very rarely breaks a timing
belt, even when people go past the recommended change mileage.
Its not freewheeling (the first-gen 3.5 was, but the 2nd gen and 4.0 are
not). However, it really does appear that the belt nearly never breaks
on these engines. Its sorta like the opposite of the Spirit R/T engine
that ate a belt every 10,000 miles, I guess ;-) I've seen one 3.5L belt
fail due to extreme neglect (well over 150k miles) combined with the
water pump failing and chewing up the belt. But I've also seen a
waterpump fail and the belt *not* fail despite getting smoking-hot on
the seized water pump pulley. The engine started to overheat due to the
stopped waterpump and the driver (my wife) pulled over before the belt
or the engine was damaged.
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