Strange grinding while under load.

[jrobb2007]

O4 with 5.4 and 4wd. While driving up hills or putting much of any loadon the engine there is a grinding sound coming from the drive train. If I back out of it it goes away. It also doesn't make any noise at cruising speed. Any help is appreciated.

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[waldo]

Does the grinding stay constant with the speed (faster = louder) or does it change when the truck shifts?

 

[jrobb2007]

Does the grinding stay constant with the speed (faster = louder) or does it change when the truck shifts?

It's stay constant with speed gear and rpm change sounds alot like brake rotor grinding.

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[waldo]

Could be diff bearings, our trucks are notorious for them starting a horrible grinding hum that's gets louder the faster you go but quiets down a bit when you get of the gas.

 

[jrobb2007]

That's sounds like it to me were is that hearing at

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[waldo]

Inside the rear differential. If you go with a good set of timken bearing your looking at about $300 (including the axle bearing and all the seals) but it's a mother to get it done (just did mine last week) you'll have to remove the rear wheels, brakes and bearings. Pull the axles and drop the case.

 

[jrobb2007]

OK thanks so much for the input my mechanic is going to put in a call to a local axle. Shop and see how much labor is going to run me. Truck has 208k I'm trying to get another 20 to 30k out of the motor before I scrap the whole thing.

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[waldo]

One easy test for that I found that work pretty well is get on the highway in the right lane near the center wall, lower your drivers rear window and hit the gas you'll hear nice and loud reflecting of the dividing wall. Get of the gas and it will quiet down substantially.

 

[waldo]

Left lane**

 

[waldo]

I drove the truck like that for 50k miles before I finally fixed it, figured I would regear and install an arb air locker while I was in there.