drivetrain noise when i let off the gas - JeepForum.com
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Unread 03-09-2010, 11:09 AM   #1
leolufse
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drivetrain noise when i let off the gas

When I'm on the highway and let of the gas and coast I begin to hear what sounds like roaring tire noise. If I put the gas back on, it goes away.
Its not super loud nor does it sound/feel like anything is "loose".
The jeep is a sport with the normal d30 and d44 axle combo, 3.73 gears, and 6 speed manual. Very low miles (22,000).
Its got brand new tires and all fluids changed and none of that made a difference.
Perhaps it is normal, but my 01 didn't seem to do this.
Is there something I should check?



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Unread 03-09-2010, 11:36 AM   #2
Hotrod97z
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An incorrect ring/pinion setup is possible, but not likely and shouldn't be an issue if it only has 22k miles. It could be a bearing or a U-joint. Have you checked the diff fluid to make sure its full? Is it coming from the front/back/both? Have the gears been changed? How loud is it? All terrain and Mud terrain tires have inherent noises.
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Unread 03-09-2010, 12:43 PM   #3
Ulumanati
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I've got the exact same problem and was told it had to do with the rear pinion bearings.. Either going bad or lost their preload. And mine only has 20k miles too which is why I was surprised
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Unread 03-09-2010, 12:49 PM   #4
VanBCguy
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Can you describe "roaring tire noise" in more detail?
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Unread 03-09-2010, 02:05 PM   #5
ps49556n
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We need more detail of this noise...I know when I am driving there is always noise when you are in between putting torque to the drivetrain and no power at all...this is the trans making noise.
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Unread 03-09-2010, 04:00 PM   #6
leolufse
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Its subtle, but if anything I hear it more on the right (passenger) side and rear.

The jeep has stock suspension and gears. The noise is there when I let of the gas in gear. Pushing in the clutch doesn't affect the noise. If I power back on the gas, it stops. If I let of the gas its there again.

When I say roaring tire noise, think of mud terrain lugs rolling on asphalt. Its not my tires because the sound stops when I stop coasting. It is a very on/off.

I had a bad wheel bearing on a car once and it was very different than this.
It would get louder with speed and coasting or power didn't make it stop.

I would guess ring and pinion noise from the rear, but the fluid is fresh and full. I changed it with RP, but it was doing the exact same thing on the stock fluid. The RP didn't make it worse or better.

Tell me about "rear pinion bearing pre-load". Is this somethig I can check/adjust?
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Unread 03-09-2010, 04:12 PM   #7
Ulumanati
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Yes what your describing is exactly what I have. Its like a rumble as soon as you let off the gas, they thought it was my tires but I verified that it isnt that or my driveshaft for that matter. The only thing is that mine happens anywhere from 30-40mph, if i let off the gas at a lower speed it doesnt happen for some reason. WHat speeds does yours happen at?

The preload has to be checked by a gear specialist who knows what they're doing, they gotta inspect the bearings to make sure they aren't going bad, and to do that they gotta open up the rear diff.
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Unread 03-09-2010, 05:30 PM   #8
NorCalCon
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Does the Jeep have a cold air intake, or anything other than the stock setup?
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Unread 03-10-2010, 09:56 AM   #9
leolufse
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Quote:
Originally Posted by NorCalCon View Post
Does the Jeep have a cold air intake, or anything other than the stock setup?
I have a banks cat back exhaust that pops and grumbles when I let off the gas, but this noise is not related to that.

Stock air intake and stock everything else.
I guess I'll just have to live with this mild noise until it gets to the point I can pinpoint exactly where it is and then figure out what it is.

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Unread 03-10-2010, 10:37 AM   #10
NorCalCon
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My cold air intake makes a sucking air roaring noise when I let off the gas at speed. I just replaced a unit bearing that gave a roaring/grinding sound only when I was coasting. I first heard it when I was getting off the freeway.
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Unread 03-10-2010, 11:22 AM   #11
Hotrod97z
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Just drive it and see if it gets worse.
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