I know noises can rarely if ever be solved without hearing them. However, I have some symptoms that may give someone a clue as to what is causing mine. Mine happens after I have driven about 15 miles at normal speeds. At that point I will drive about 10-30 MPH for about 5 miles and then I get the grinding sounding like it is coming from under the hood. I can stop, open the hood and can't hear the grinding anymore. Rev it up no noise. Get back in truck and take off and it happens again under load. Sound remains the same regardless of RPM's or slower speeds. Coming back home from the 15 miles at normal speed and no sound. I have about 2 miles to my house from there and the noise will return at slow speeds in my neighborhood. I drove it yesterday to my BIL's shop and nothing. Mechanic and I went out driving slow and nothing of course. Never did it at all.

I have replaced the fan clutch and the A/C clutch, bearing and pulley. Took it out again to the 15 mile point and slowed down and it started doing it again. All pulleys work as they should and are secure. The noise is not coming from the drive train and wheel bearings are good. It clearly sounds like under the hood to me. I certainly don't expect anyone to tell me what is causing it but does anyone have a recommendation as to what I could check based on the unusual symptoms that seem to be causing this. Sandy
Lastly, I recently took the pulley off the smog pump and bypassed it with a shorter belt. I left the smog pump in place. I have no diagnostic codes.

 

Pull the belt off and spin the pulleys by hand. See if that causes any sounds

 

Thanks. I have done that and everything goes properly and noise free. BTW my 460 uses two belts FWIW. Anything else?

 

Transmission. My E4OD would grind on occasion before I replaced it.

 

My fluid is right on full and is bright red. I have had just a few hard shifts lately. I ran codes again yesterday hoping something from the e4od would show up. No codes. I will try different gears next time it happens including reverse. Thanks for the suggestion. Anything else I can check? Sandy

 

Took it back out today and the noise started about the usual time. I got some good sound bites but I can't get them to work here. Does anyone know how I can post them? I tried all gears including neutral and reverse and the noise was in all gears. I measured the transmission temp and it was about 175* Got home and let it idle in the driveway a few minutes and could not recreate the noise and then drove it around the block and nothing. I am really stumped. Sandy

https://www.ford-trucks.com/forums/a...8&d=1571600239

 

https://download.cnet.com/ios/clyp/3...0349275-1.html

 

SOUND BITE OF THE TRUCK NOISE

This seems to work. Give it a second to play automaticlly or touch the play button.

https://vocaroo.com/i/s04XyK6lpAMO

 

Well that sounds like satan trying to come through the floor.
But anyway, is that with steady speed and throttle or varying throttle?

 

It is a dead stop. I get going where you can hear the noise then I let off gas coast a second and gas it again then let up.

 

I hate trying to diagnose driving noises. I suppose you could try putting the rear on GOOD jack stands, pull the tires to cut down on rotating mass and have someone run it through the gears to see if you can pinpoint it. I had to do that on my tahoe when the internal shoe for the disc brake parking brake came loose.

 

I think I may have found the problem. Drove the route today and no noise. Yesterday I pulled my two belts and rechecked the pulleys. I noticed since I replaced the left belt when I deleted the smog pump, it had a little more slack than the right side belt. The right belt operates on the tension pulley. The shorter belt I put on is tightened by the alternator. I adjusted the shorter belt tighter to match the right side. That had to be the issue IMO since this is the first time the noise hasn't happened.

If the belt was somewhat loose, why would the noise start after the engine got hot like in my description. In other words should I expect to have a failing pulley or would the belt just being loose cause a pulley to make the noise after driving for a while? Sandy