Engine rattle in 2002 V8

[walleyek]

My son's Explorer has 135k miles. Haven't had any engine issues until yesterday. Very loud rattle was coming from the top of the engine, accelerates with the gas pedal. Rattle goes away when I put the truck in Reverse. I am not mechanical. Could someone listen to the attached file and tell me if the engine sounds like it's shot? Thanks!

 

[Number4]

Might be a broken timing chain guide. Pull the valve covers and see if the chains are loose. I've heard a busted guide that sounded like engine knock. The guide is just smacking around.

Also inspect the followers (rockers) while off.
And stop driving it at this point.

 

[imp]

Might be a broken timing chain guide. Pull the valve covers and see if the chains are loose. I've heard a busted guide that sounded like engine knock. The guide is just smacking around.

Also inspect the followers (rockers) while off.
And stop driving it at this point.

@Number4
But, but, would it hurt anything to drive it awhile only on Reverse? imp