Rear-end Howl

[deanpence]

I've got a really good howl coming from the rear end. Starts low and soft, but by 55mph or so, it's higher pitched and loud enough to make conversation difficult. It lets off a bit by the time I hit 70mph, but not much. The howling only changes with speed, not with turning.

 

Thanks to a bunch of you on another thread, I got my rear diff (LSD) oil changed (I couldn't get the damned plugs open myself), and the mechanic didn't mention anything about water, excessive shavings, or low oil level (though I didn't ask either). This solved my problem of low-speed rumbling/shaking when turning, but it doesn't seem to have solved this noise issue.

 

From what I've gathered by searching the forum, the consensus seems to be that bearing problems are pretty rare on Pathfinders, but that it's possible the rear diff has some damage.

 

One shop I asked said they would need at least several days to diagnose a rear-end problem. This just isn't feasible, money-wise especially. I'm very new to this stuff, but I'm smart and willing to learn and get my hands dirty.

 

Can you guys recommend how I should go about troubleshooting this?

Edited August 15, 2011 by deanpence

[Cuong Nguyen]

Did the mechanic put in the right fluid that's made for a LSD?

 

Can you pinpoint where the howling/whining is coming from? left side, right side middle rear? My guess it's a wheel bearing. If the diff was low in fluid oil won't make it to the wheel bearings to keep them lubed. If the shavings are big enough, it could damage the wheel bearings and score the race.

[sewebster]

The wheel bearings are outside the diff, near the wheels, but I think you just mean the bearings in the diff... those could be responsible, or something else in there I guess. If you jack the rear end you can check for play in your wheel bearings by grabbing the tires and trying to wiggle them around. If they are tight (no play) then it probably isn't your wheel bearings.

 

I assume you're sure it's not some exhaust tone or something... It changes with vehicle speed only, not engine speed, right?

[deanpence]

@Cuong: I've tried, but I can't pinpoint an exact location—or even a general location except the back end. For a while I had trouble even telling it was coming from the back end when it was loud.

 

If it's a wheel bearing, is there any way I can tell without disassembling the axle?

 

@sewebster: Well, I meant the wheel bearings, but if it's the diff bearings, is there any way to tell? Disassembly seems like a horrible idea.

 

I only have the one jack used for tire changing. I suppose it may be time to get decent jack stands. Any recommendations?

 

I'm not positive it's not the exhaust, but the sound definitely only changes with vehicle speed, not RPMs, so it seems unlikely (from what I understand).

 

I found a few issues that may match from the Hayes manual's troubleshooting section:

 

Under Driveshaft, a "metallic grating sound consistent with vehicle speed" is due to "pronounced wear in the universal joint bearings". This doesn't sound like a metallic grating sound to me, but I may just not know what I'm hearing. I took a look at the driveshaft's three U-joints; is there any way to identify wear?

 

Under Rear axle and differential, a "noise - same when in drive as when vehicle is coasting" could be caused by tire noise, front wheel bearings (loose, worn, or damaged), insufficient differential oil, or a defective differential. It looks like I can get the the outer wheel bearing without taking off the wheel hub, but the inner bearing requires taking off the hub, but I have nothing to adjust the endplay with when putting the hub back on.