Reading through a few past posts and threads I saw something that caught my attention... the 4.0 engine knock topic... While reading it, it sounded an aweful lot like what I am getting, then I saw that it is only happening at cold operating temperature... Is this (pri. tensioner) what is probably causing a rattle or chatter while the engine is slack, like coasting under very little load down the highway? As soon as I put it under load it quiets up and runs like a champ. If this post is redundant I apologize. Worst case scenario I keep it to the floor everywhere I go.

 

The belt (or chains in this case) loosens up a bit--it expands--as it warms up. Bad tensioner = well, you get the point.

You can floor that bad boy, but sooner than later, that chain will move in ways it should not at highway rpms and leave you stranded.

 

What year is your Ranger?

The 4.0L OHV (up to '01) and the 4.0L SOHC ('01+) can make noises for different reasons.

 

Its an 04. I have about 28000, (I live 80 miles from work) on it and besides the noise its running great, no other complaints.

 

it should still be under warranty. I would take it to the dealer and have them check it out.and give you a loaner for work.

 

I too had a similar problem with my ranger, however, after taking it to the dealership, it was discovered to be a loose rear converter shield. just a thought.