Tire hum or???

[Kevin B.]

This is a new one for me. I've got a hum/whine from the rear that sounds exactly like a set of big meaty MTs. But I don't have big meaty MTs, and I've had the noise through multiple balances and rotations, and here's the kicker, it's only apparent when I'm on the gas. It fades off when I coast, it comes back immediately when I touch the gas pedal again. It's almost like the act of accelerating pulls one or both tires just slightly off kilter with respect to the direction of travel and causes the howl, except I don't have any funny tire wear either.

I'd blame it on something in the drivetrain, but I do not have any play or leaking gear oil at the rear wheels like I'd associate with a bad wheel bearing. I don't have any play at the ujoints or going into the diff either. I don't know what else I can do to isolate this. Anyone have any insight before I tear it down and start throwing parts at it?

'01 Supercrew with the 9.75 axle, in case it matters.

 

[Jay5.9L]

My vote is a bearing. Out little Subaru had the same sound and after muitple tire rotations it was a bearing.

 

[Jack-It]

in our opinion:

The way you describe the noise, makes me think that you're experiencing possible ring and pinion noise (gear howl). Tires normally don’t sound different while under acceleration or just cruising. If it is ring and pinion noise, this can be caused by the differential carrier moving a little (bad bearing, case or housing wear), pinion movement (bad bearing, pinion nut backed off), contaminated fluid (water), or even aftermarket gears (not set up proper or straight cut aftermarket gear set). If you have had any work done on the rear differential that could help diagnose what is happening.

To properly diagnose, verify no movement of the pinion, pull the cover and inspect the internals, run a gear pattern check, make sure the fluid is not milky and that it does not contain any visible metal flakes in it.

 

[idahoyj]

My Nissan Armada did almost the exact thing. Except mine would change sounds when I put pressure on the steering left and right. I jacked it up and checked for slop in the wheel bearings. Nothing. I was convinced it was the diff... So I let it go because I did not want to get into the diff. Then a few months later, I decided to do brakes. When I jacked it up, the right rear wheel had so much slop in it, I'm surprised it didn't fall off! I replaced the wheel bearing along with the brakes, and the sound was gone. I guess when I had checked it earlier on, it just wasn't loose enough to feel the slop, but it sure went down hill fast!

 

[DAA]

So not anything new to add, just that maybe make sure it's really not a u-joint. Mine was making a similar noise - only when on the gas. Suspected u-joint. But grabbing the driveshaft and checking for play, I couldn't detect any. When the sound got worse and I decided to start taking stuff apart to diagnose, the second I unbolted the driveline I could see slop in the u-joint. But not until I dropped the dive shaft.

- DAA

 

[rholbrook]

I had the same thing and mine was a bad wheel bearing years ago.

 

[Kevin B.]

Definitely the bearings or the driveshaft or the diff then, got it .

Thanks for the input everyone, I appreciate it. Long weekend coming, I'll dig in and see what's what.

 

[SLC97SR5]

Does your truck have a carrier bearing for the rear shaft?

If that or the isolator is worn that could explain the pitch change dependant on throttle because it allows the shaft to travel outside of it's fixed rotation.

 

[Kevin B.]

No carrier bearing on this truck. I think that's just the extended cab long beds.

 

[RogueJeepr]

Did ya find out what was making your truck run funny during the swell trip ?

Sent from my H1611 using Tapatalk

 

[Kevin B.]

Did ya find out what was making your truck run funny during the swell trip ?

Sent from my H1611 using Tapatalk

A combination of things, I think.

 

[dutchman]

I smell sarcasm...

 

[DAA]

Smells like awareness to me.

- DAA

 

[Kevin B.]

I suspect I already know the answer to this, but is there any point in trying to take a pattern on the gears with the carrier still in the housing?

 

[I Lean]

I suspect I already know the answer to this, but is there any point in trying to take a pattern on the gears with the carrier still in the housing?

That is the only way to run a pattern--you're testing the mesh of the gears, so they have to be installed in the housing.

 

[Kevin B.]

That is the only way to run a pattern--you're testing the mesh of the gears, so they have to be installed in the housing.

Maybe I'm using the wrong terms. This is a Ford 9.75, so it's not a drop-out third. Can I take my pattern with the whole mess still in the axle housing, or do I need to yank it and get it on the bench?

 

[idahoyj]

It all needs to be in the axle housing.
Over simplified instructions- drop the cover and oil, clean the teeth, paint some teeth, look at pattern.

 

[Kevin B.]

Groovy, that's easier than I feared.

 

[Kevin B.]

I feel like I see good depth and good lash on the sloped (drive?) side, and bad depth and bad lash on the other. And that makes no sense, so somebody who knows what they're looking at tell me what I'm looking at please.

 

[BCGPER]

I'm on my phone, so take that into consideration. Looks horrible to me, I'll bet you have bearing issues