Engine whine at highway speeds

[Brynjminjones]

I've been driving my '91 GW a lot more lately, so of course I'm noticing a lot more wrong with it

For a while now it's had a noticeable whine from the engine bay at highway speeds.
It sounds almost exactly like a power steering pump, so I'd always assumed that's what it was.

Today though I paid more attention to it, and I'm now starting to question if it actually is the pump.


When driving along at constant speed, there is a definite whine that changes with RPM.
It isn't affected at all by turning the steering wheel, and my power steering doesn't whine when maneuvering anyway.

The whine goes away almost totally if you come off the throttle, and gets louder the more load I apply.

It's not always there. Sometimes it will quiet down for 30 seconds or so, then gradually fade back in.

It's definitely a whine. Not a whistle, squeal or air sucking noise.

My oil pressure at speed is good. It's usually somewhere between 50-60psi on the gauge, although I have noticed that it slowly varies in that range whilst driving at constant speed.
Sometimes it also seems to drop slightly when I get on the throttle.

Here's a video taken the other day that just catches the noise. It first becomes audible at around 20 seconds if you listen very, very closely. It gets a bit more obvious around 27 seconds.
Don't pay any attention to the rear axle noise you can hear!

https://youtu.be/p_agPvOHZLI

[SOLSAKS]

I can hear it, kinda sounds like feedback on a microphone,....

and like the sound I hear constantly since losing my hearing in left ear !

I wonder if it is electrical, like alternator noise, sometimes fixed with an inline filter,....

was the radio turned completely off ?

does not sound like a pulley,....or wind noise,...

someone on here will have a better diagnostic ear and mind than me !

beautiful country road !!!

dave in NC

[Brynjminjones]

Thanks Dave, yeah it's a lovely road. Goes right around a lake but you can't get close to the water at the moment due to our lockdown!

I can see how it sounds like an electrical noise, but I'm reasonably confident it's not. I definitely agree though that it's not wind noise!
The radio is totally off and it sounds like it's coming from the engine bay.


Honestly, it sounds identical to a power steering pump whine, it just doesn't seem to behave like one!
I really can't figure out how it's affected by engine load.

[Ristow]

check the transfer case oil.

[PlasticBoob]

Sounds like the whine of an old stick shift transaxle. I've seen a few vehicles behave exactly like that regarding the load situation. I'd say transmission output, transfer case, or differential. Probably some sloppy gears or loose "thrust areas"/bearings somewhere. I would not be concerned yet.

Have you checked all the fluids from the trans on down to the differentials?

[Ristow]

yah,pull the drive slugs out of the front hubs,verify 2wd mode engaged and go for a spin.

[babywag]

Don't ignore rule out rear axle bearings either.
Losing a shaft @ speed is no fun!
They don't always exhibit typical bearing growl and bearing noise can travel/be deceiving.
I lost one once and always check them regularly on FSJs now.

[Brynjminjones]

Thanks for the advice all!

I've done a bit more listening the last couple of days, and can confirm that the noise is definitely related to engine speed, not wheel speed.
I've not had a chance to check fluids or anything else just yet so will report back once I have done.

There is also noise from the rear axle which isn't what I was originally trying to diagnose, although it is audible in the video above (most obvious from around the 12 second mark) and I could do to sort that out too!
The rear axle noise is a kind of low "whoosh, whoosh, whoosh" with each revolution, which eventually stops becoming noticeable once you're going above maybe 50.
It doesn't change at all as you go around a corner and it's not affected by being under load vs coasting.

[PlasticBoob]

Thanks for the advice all!

I've done a bit more listening the last couple of days, and can confirm that the noise is definitely related to engine speed, not wheel speed.
I've not had a chance to check fluids or anything else just yet so will report back once I have done.

Have you tried driving it with the belts off, one by one?

There is also noise from the rear axle which isn't what I was originally trying to diagnose, although it is audible in the video above (most obvious from around the 12 second mark) and I could do to sort that out too!
The rear axle noise is a kind of low "whoosh, whoosh, whoosh" with each revolution, which eventually stops becoming noticeable once you're going above maybe 50.

LOL, maybe a tire?

[Ristow]

I had a loose center cap make noise like that.

[Brynjminjones]

I feel a bit stupid about this now - I'm pretty sure it is the power steering pump after all!

It didn't previously seem to be affected by turning the wheel, but I think now that's because I don't tend to turn the wheel far enough to stress the pump whilst at high enough RPM to cause it to whine.

I accelerated harder around a sharp corner the other day and it definitely did seem affected by steering, so pretty sure that's what it must be. My XJ does the exact same thing, I just notice it more as I tend to drive that much harder!



Now I guess it's time to investigate the rear end noise a bit more.

I originally suspected it was a tire out of round, as the Jeep had covered about 1000 miles in the 5 years before I bought it.
I've since had new tires though, plus covered nearly 20,000 miles, and the noise hasn't changed!

I also don't think it's a center cap - I check those reasonably frequently because I'm paranoid about them falling off!


Can wheel bearings make this kind of noise, without being affected by cornering?

[PlasticBoob]

Can wheel bearings make this kind of noise, without being affected by cornering?

Ehhhhhhh.....maybe. Hate to say this, but could also be a pinion bearing or....I believe there are also two inner differential side bearings as well.

Dangerous procedure I highly advise anyone against doing under any circumstances: I have put vehicles securely on jackstands, then put the car in drive and checked to see if the noise went away. Solved a major issue this way once!