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Unread 09-12-2013, 06:11 PM   #1
nodoze
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noise while accelerating/decelerating around 60mph?

Hi guys

Today I noticed a noise while driving. While I'm driving with my foot on the gas, I don't hear it. Coasting with the foot off the gas I don't hear it either.

Where I DO hear it, is right before I take my foot off to coast, and right when I just start pressing the gas pedal to speed up again. Barely press the gas, hear the noise. Press more on the gas, and the noise goes away. Holding the gas pedal barely pressed and I can make the noise continuously happen.

The noise sounds like a humming kind of noise, almost metallic in nature? I first noticed it around 65mph. It also appears quieter at 60mph, and hardly noticeable around 55mph. Below that speed I don't notice it at all.

Has anyone experienced this before? Any pointers on where to look at, or how to diagnose it?

I appreciate the help!

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Unread 09-12-2013, 08:31 PM   #2
gmtech22
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May be the resonance from torque converter engagement
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Unread 09-12-2013, 09:31 PM   #3
rlcii77
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You might check the driveshaft u-joints, transfer case fluid, diff. fluid... Can you tell if the sound is coming from any location in particular, front, rear, center? Sometimes it can be difficult to identify where the noise is originating, but the more info you can offer, the better... How long has it been since the trans. fluid was changed, and the other fluids for that matter?
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Unread 09-12-2013, 09:47 PM   #4
nodoze
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Quote:
Originally Posted by rlcii77 View Post
You might check the driveshaft u-joints, transfer case fluid, diff. fluid... Can you tell if the sound is coming from any location in particular, front, rear, center? Sometimes it can be difficult to identify where the noise is originating, but the more info you can offer, the better... How long has it been since the trans. fluid was changed, and the other fluids for that matter?
I've only had the Jeep for maybe two weeks, and today is the first I've noticed it., I'm not sure where the sound is coming from.

I've topped up the transfer case, and the rear differential is full but weeping from the pinion seal. I'm not sure when the fluids were changed last but they're all on the list to be done shortly. I remember the Trans fluid being red and not brown looking though.
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Unread 09-13-2013, 10:22 AM   #5
PolkaPower
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If it was a bearing it would make noise all the time no matter if you are accelerating or coasting.
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Unread 09-13-2013, 10:38 AM   #6
Dukcaln
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mine will do the same thing, kind of a humming sound as you described, like under acceleration at the end just as you let up on the pedal then costing its gone. I was going to check the ujoints and service the front diff and see what that will do. go from there. kinda sounds like my noise
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Unread 09-13-2013, 12:06 PM   #7
nodoze
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Quote:
Originally Posted by PolkaPower View Post
If it was a bearing it would make noise all the time no matter if you are accelerating or coasting.
So that's good news then, right?

Quote:
Originally Posted by Dukcaln View Post
mine will do the same thing, kind of a humming sound as you described, like under acceleration at the end just as you let up on the pedal then costing its gone. I was going to check the ujoints and service the front diff and see what that will do. go from there. kinda sounds like my noise
I'm going to do the same thing I think. I'll swap out the rear differential fluid and see if the noise goes away or changes. I'm going to try to get that done this weekend. I'm new to jeeps, I'm not sure how to check ujoints yet.

On the way to work this morning it didn't make any noise around 55 or 60 but it did at 65.

I was also able to kind of lean back in the seat and stick my head towards the back, and the sound definitely seems to be coming from the rear of the vehicle.
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Unread 09-13-2013, 12:44 PM   #8
PolkaPower
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Are you sure it's not the tires? Imbalanced tires would make noise during certain speeds and not others. Try swapping the rears tire to the front and see if the noise changes.
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Unread 09-13-2013, 06:36 PM   #9
nodoze
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Quote:
Originally Posted by PolkaPower View Post
Are you sure it's not the tires? Imbalanced tires would make noise during certain speeds and not others. Try swapping the rears tire to the front and see if the noise changes.
That's a great suggestion, thanks! I'll try to do that this weekend.

Another observation: The sound at 65 is a lower pitch than the sound at 75. At 75 the noise isn't louder, but the pitch is higher.

Also the noise is not constant, it only happens when i first start pressing the gas, or when I'm almost fully let off of the gas pedal.
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Unread 09-14-2013, 02:27 PM   #10
Oldfrog
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sounds a bit like a pinion bearing going out.
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Unread 09-14-2013, 06:35 PM   #11
nodoze
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Quote:
Originally Posted by Oldfrog View Post
sounds a bit like a pinion bearing going out.
If that's the case, what does that mean? I know the repair is hard and has to be done by a professional, but how long until it goes out and what happens when it does?
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Unread 09-14-2013, 06:37 PM   #12
nodoze
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Tonight I'm picking up ATF+4 and a transmission filter/gasket set, plus 70w90 to swap out the differential fluids. I'll swap the fluids this weekend or this coming week and see what happens.
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Unread 09-15-2013, 04:36 PM   #13
Oldfrog
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When my pinion bearing failed, it made noise while under a load. ( mainly when accelerating). I suppose it could also make noise any other time if it's bad enough.
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"..it's not air, it is the opposite of air... suckage so to speak."

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Unread 10-12-2013, 10:45 AM   #14
Dukcaln
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are front pinion bearings difficult to change?

also, no doze what happened after you changed the front and rear diff fluids, did it help?
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Unread 10-12-2013, 07:03 PM   #15
Oldfrog
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I have no idea. I paid a local 4X4 shop who had a good rep to swap mine out. Didnt have time to jack with it myself. It was done in 1/2 a day....and for about $465...or maybe it was $365....I forget.
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"..it's not air, it is the opposite of air... suckage so to speak."

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