2k Limited humming under load

[nycfyrman]

Under load at approx 2k rpms above 50mph I have a humming noise. I have yet to replace any parts yet. I am perplexed. It sounds like its in the pass front, but then sometimes sounds like the rear. If I apply the brakes while under load it does not change the noise so i do not think its the wheel bearings. I have greased the U-joints more than Harvey at a casting interview. Still no change. Could it be the rear diff or a worn u joint that is too far gone. Again it only makes it under load. 80mph going downhill not a peep like a lexus, add some pedal and its humming.

And save the its humming cause it doesnt know the words jokes ;-)

TIA

This place is invaluable!

 

[Bad Luck]

Wheel bearings would be a constant noise regardless of load so it's not that. It's possible that it could be the rear differential. I'd remove the rear driveshaft and try to replicate your problem in 4HI (which will really be FWD because the rear driveshaft is gone). If the noise isn't there in 4HI w/o rear driveshaft then you have narrowed it down to either the rear driveshaft or the rear differential.

 

[nycfyrman]

I was considering doing that as well. searching around it almost sounds like a u joint but then it doesnt. The noise stays the same in 4wd or 2wd so I don't think its ujoints but then again I could be wrong.

 

[brillo_76]

Rear ends will wear in time and can hum. My 98 has a warn 3rd member in it. It will start humming at 60 or so and gets louder till 70 or so.

So pulling the rear driveshaft as a test is not a bad idea at all. Also as a test. You can put 100% locus heavy duty oil stabilizer in place of your gear grease. If the noise changes then you definitely know where the issue is. However, pulling the driveshaft is cheaper then using locus.

That sound can travel and sound like it's coming from the front and cause some confusion.


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[dogtail]

Yup I 2nd Bad Luck. Pull the rear driveshaft and run it in front wheel drive, its quick elimination test.

 

[gamefreakgc]

My diff bearings went bad but it only made a humming/grinding noise when decelerating, under acceleration it was quiet. Sounds like it's probably a u-joint or drive shaft out of balance.

The front driveshaft can also spin in 2WD FYI. Though it's rather short and rarely goes bad like the rear one. I would try driving in 4WD first (if you have it of course) to see if that changes the noise and then pull the rear (once again, if you have 4WD) driveshaft to isolate the noise.

I have a humming noise I get from 35 MPH to 70 MPH that I never figured out. It's either my front wheel bearings or the front diff. Everything else has been replaced or eliminated at some point. Going to have mine regeared at some point so that'll tell me if it's the diff or the front wheel bearings.

 

[Cree]

If it sounds anything like this, your 3rd member is shot.

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[brillo_76]

If it sounds anything like this, your 3rd member is shot.



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I hear your tires more then that bearing noise.. However, yes you have some bearings wearing out.


Mine is different then that. I actually think mine is teeth mesh wear in my 3rd member.
[MENTION=95040]Cree[/MENTION] are you going to just replace that member or replace the bearings that are warn in it. Just curious how many miles on the member.

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[Cree]

That was 100% pinion bearing noise you were hearing. It was awful from about 35 to 55. I was going to replace the entire rear end since I was pretty sure the housing was warped, but the frame broke in half when I jacked the truck up to replace it so the whole damn thing went in the trash.