Loud Humming Noise when I let off gas, coasting 30-50 mph? - JeepForum.com
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Unread 09-21-2011, 09:49 AM   #1
pmarascal
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Loud Humming Noise when I let off gas, coasting 30-50 mph?

I've been doing a lot of front end work the past 2 weeks, searching out a sound I had. So you might have seen about 50 posts from me lately asking random questions, sorry . I can't hear my original noise so Im praying it was front U-Joints I replaced, but maybe I just can't hear that noise because now I have this horrible loud humming noise when I let my foot off the gas and coasting around 30-50 mph.

For background, both DS were rebuilt 6,000 miles ago, this week I just did both front axle u-joints, passenger upper Ball Joint and replaced bushings in my front shocks. I can't help but be paranoid because these u-joints and ball joints were the first job I've ever done completely alone. Don't get me wrong me and my dad have done pretty much everything on either of my last 2 jeeps, but now I'm down at school trying it by myself.

I didn't notice the sound until the day I put in u-joints and that ball joint. Even then, it was not bad and barely noticeable. Now it is so loud that it goes over my radio, and its only when decelerating. So I take my foot off the gas and the sound comes in, then I can barely barely press the gas pedal and it will completely go away. Its from about 25-50, but I notice it to be a little bit louder when coasting up at 50.

From what I've been seeing, a lot of people seem to be told by their dealer that the sound is normal... wtf... definitely not normal. Its almost like my tire humming, but way louder, and controlled by accelerating/decelerating. Anyway I see a lot of talk about it coming from the rear Pinions, maybe a bearing going bad. How can I pinpoint front or rear diff?

Also fluid was changed in rear about 3,000 miles ago and I inspected for any tooth damage, and front diff was changed today. How much can I expect for a mechanic to diagnose if its a pinion bearing, and then replace it?

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Unread 09-21-2011, 11:31 AM   #2
4wdjeepguy
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That sound will go away with a SYE and CV d-shaft
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Unread 09-21-2011, 12:16 PM   #3
pmarascal
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But its never been there before. And I've got a CV in the rear, no SYE though. So my TC is dropped with a piece of 1" stock tubing, so I haven't had those kind of vibes since then (year ago) and I don't have bad vibes now really either?

I guess my next step is to remove a drive shaft, go test it out. See if removing one of the shafts changes anything. Otherwise pinion bearing is what I've been hearing? I just can't tell if front or rear. Heard maybe front because its when i let up off the gas is when I hear it.
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Unread 09-21-2011, 03:15 PM   #4
pmarascal
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I forgot to point out that my tranny mount has 2 broken bolts, so only 2 holding it on. NY rust and I had todrive it. I'm gonna check it with a pry-bar to see if my tranny wiggled around at all, but could this have caused my driveshaft to get screwed up, perhaps blew those Ujoints in only 5,000 miles?
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Unread 09-21-2011, 07:18 PM   #5
relgnarw
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I've had unit bearings growl/roar when they are going bad. Could yours be going bad? I know you've thrown alot of time and money at this, but have you considered the bearings?
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Unread 09-21-2011, 09:13 PM   #6
pmarascal
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Forgot to mention I had wheel bearings replaced both the front. Is that what you are talking about 'unit bearing'? Or is that something else?

All recommdations are helpful, my dads saying I should let the noise be until something goes wrong, says that's the only way sometimes. But I'd rather not do that especially if it's something that could mess up my gearing
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Unread 09-22-2011, 02:24 AM   #7
relgnarw
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Quote:
Originally Posted by pmarascal View Post
Forgot to mention I had wheel bearings replaced both the front. Is that what you are talking about 'unit bearing'? Or is that something else?
Yes those are what I'm talking about. As far as what the noise could be, without hearing it, I couldn't guess
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Unread 09-22-2011, 04:28 AM   #8
lurch9
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I had a similar noise a few weeks ago coming from my rear axle. Mine turned out to be carrier bearings. Lucky for me, they were covered under warranty.
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