I have done a search on this subject and only found info about replacing the belt and/or tensioner. Im not really sure that that is the problem. It sounds like a bad idler pulley or something. It get obnoxiously loud the higher the RPM's and it starts around 2000 RPM's. Even when I just rev the motor with the thing parked it does it. The ONLY performance mod on the truck is a gibson exhaust and that has been on there for a while now.

Any Ideas??

Thanks

1998 F-150 w/ 4.6 and 5spd

 

Id try the belt first if that didnt work id take it to the closest ford garage and have them check it out
Could be something bad or it could turn out to be something very simple!!
JJ

 

I dont think that thats the problem because everyone else that had that problem said that it was happening when they would start up the truck and all throughout the RPM range. My problem only happens in the upper RPM's. Plus it doesnt sound like a belt squeel. It sounds more like a rattling noise. Kinda like a bad or loose idler pulley or a bad tensioner.

Thanks though

 

If you think it is a bad pulley and not the engine why don't you test them?

take the belt off and turn each one by hand and see if they feel "gritty" if they do or they turn slowly you have most likely found your problem.

if it is that loud and you can duplicate it while looking under the hood you should be able to pinpoint it fairly easily.

good luck.