WoooWoooWhirrr sound at speed

[87MJJeep]

Now that I have safe tires on my MJ again, I've been driving it to work this week. There is a sound I had forgotten about, and I think it's more noticeable now that the carpet and padding it out. Everything is louder now...

 

It sounds like it's coming from the rear half of the truck, but I am not sure. I seem to hear it the most from ~24-45 MPH. It's a wooooo-wooooo whirrrrr sound. It is vehicle speed dependent, not engine RPM dependent.

 

The truck has 73K miles on it, and it is a 4x4. It drives straight, and I see no sign of it ever being wrecked. My first suspicion are wheel bearing in the rearend. But I've never had a 4x4, so I don't know if it's noise from the transfer case/etc. What areas should I focus on?

 

It's made this sound with multiple sets of tires. Any pointers would be appreciated!

[whowey]

Thanks for the laugh... the title made me chuckle.

 

Normally a T-case operating correctly make no noticeable noise.

 

Rear wheel bearings or pinion bearing would be my guess at a culprit.

[87MJJeep]

Thanks for the laugh... the title made me chuckle.

 

Normally a T-case operating correctly make no noticeable noise.

 

Rear wheel bearings or pinion bearing would be my guess at a culprit.

 

Glad to make someone laugh. :D The woooowooooowhirrrr doesn't change tone very much if I let off the gas. The sound continues. Do you think a pinion seal sound would come and go with load similar to a whiny set of gears? I've had experience with noisy gears in three different vehicles. They all were speed AND load dependent. And total PITAs. :fs1:

 

EDIT: Wait a minute. I just realized your username. I think the noise sounds a little like it, too! :yes:

[jpdocdave]

well, my first thought was front hub bearing. you gotta make sure its not just traveling. try swerving from right to left while driving, this transfers the load from one side to the other and will make hub bearings change noises. if it changes noises you may be able to locate it better. pinion bearings are very common, but "usually" will change with drive line load, so if you put it in nuetral while driving they usually quiet down if its pinino bearings. never ever heard a rear outer wheel bearing make noise yet, but its possible.

 

here would be my first step after driving it. put the rear axle on jack stands securely. have a partner put it in gear and slowly give it gas till you reach about 35 mph or so on the speedo. listen to the rear diff, you can also put a screwdriver to the cover and to your ear. little noise is normal, if its as loud as you're saying if you put a screwdriver to your ear on the cover you will not mistake it if its coming from there.

 

please don't kill yourself by following my adivce, :smart: only do this if your comforatable jacking a vehicle. use two heavy jack stands, not no little 2 ton or so crap. chock the front wheels, and shake the truck to make sure its secure before you get under it.

[87MJJeep]

Thanks for the actions to perform, Dave. I will try to do some of that this weekend. (after I install the foglights. hehe.)

 

I am really particular about how to jack and support a car. I had to pull a transmission once. I just didn't like the idea of wiggling a transmission out with the front suspension on stands. That's not enough contact area for parts that change angles under load! I made two blocks out of overlapping 2x4s that the front tires sat on, then I had those beefy jackstands under the rear axle. ;)

[jpdocdave]

ahhh, priorities. fog lights before bearings :rotfl2:

 

just joking, let us know how those work to, and let me know what you find with the bearing noise.

[87MJJeep]

ahhh, priorities. fog lights before bearings :rotfl2:

 

just joking, let us know how those work to, and let me know what you find with the bearing noise.

 

After SuperWade2's heater control valve thread, I may be bypassing a heater control valve and replacing some hoses before checking on the wooowooo noise! Maybe I should "engineer" some pipes into the heater core inlet/outlet hoses, so when it finally craps out, I can just turn a valve to bypass it. "What's that?" "It's my manual heater CORE control valve." :nuts:

[jpdocdave]

sounds like this noise has been going on for a while, i wouldn't keep putting it off too much longer, if it is in the rear end you wanna catch it asap, replacing bearings is a lot cheaper and easier than ring and pinions and/or housing.

 

i think you got too freaked by that heater valve. tons of vehicles have them, not just older jeeps. they are cheap to replace when they go bad, and if you pay attention i'd say almost everytime you'll notice a small leak before they blow out. i've had two that way. honestly, thats the first time i've seen one just completely blow out without warning. on my 96 xj i saw the small leak and put it off for a week before replacing, and that didn't happen.

[CWLONGSHOT]

I would look hard at your universals, @ both ends of the rear drive shaft. You will need to remove it to look correctly. Then check the fluid in your T-case. If nothing else, its probably due for a change anyway.

 

 

CW

[87MJJeep]

Thanks for the advice Dave and CW.

 

Foglights still come first! At least it'll look better when I sit and stare at it. :D

[mvusse]

Even though it sounds unlikely, I would not be surprised if it is the gears in the rear axle. Oil could be low, or pinion shaft could have gotten messed up.

[87MJJeep]

A slight update. Either I am going cuckoo, or I can hear the noise as slow as 15-20 mph, too. It may be more of a whirrrr than that wooowooo I first reported. :nuts:

 

I put it on stands Saturday morning, and with my assistant holding it at 45 mph, and with a automotive stethoscope placed all around the back side of the diff, the axle tubes at various spots including as close to the ends as possible, nothing sounded out of the ordinary. I heard the same "normal" noise no matter where I put it.

 

Transfer case leaked fluid out when I removed the upper plug, so it's not low. I was expecting it to be low considering it appears to be weeping some fluid from the seal that goes between the case's two halves.

 

Back to the rearend, I observed something. The left tire clearly spun faster than the right one. I knew from testing the brakes in the rain, if I jab the brakes, the right rear locks up. It once locked in a semi-panic stop on dry pavement, too.

 

When applying the brake with it on stands, the left rear definitely took longer to slow down. Some may recall I posted here several weeks ago about a squeak-type noise when the brake is applied. I would have bet money it was coming from the front of the truck, and I even wondered it if the was pedal linkage. Nope, it comes from the left rear drum. If anyone has any thoughts on any of this, let me know. I've done all sorts of things on other cars front disc setups, but I've never done anything other than look at a drum brake.

 

I wonder is the right drum too "tight" or is the left one too "loose?" With the screech/squeak I hear, I imagine it's the latter.

 

CW, I have not disassembled the u-joints yet. I haven't forgotten that. And I need to check the diff fluid level, though as normal as it sounded, I doubt that's an issue.