Shortly after buying my truck I heard a rattle from underneath, I suspected catalitic converter shield or something loose but found nothing. I then took it to my exhaust guy, it did not take him long to find the problem, each converter had a tag spot welded on them , the welds broke and there they were,sliding around were I could not see them, between the shield and conveter. I hope that this may help someone out.

 

I have a 97 F250 and recently began having the same problem.
Did you have it corrected and if so, was it fairly cheap?

 

My 97 f150 does the same thing, but only when idleing. When I give it gas, it quits.

Josh

 

Josh, mine does as well. I suspected something in the a/c system or heating system... but it doesn't matter if it's on or not. Once I put it in park it goes away. It's very odd but i can't find anything loose.

 

when the 97 model exhaust was recalled for making rims black i has the 5.4L lightening exhuast from the 98 models put on it. dad has connections so it was no cost to me