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Discussion Starter #1 (Edited)
Hey everyone, been a LONG time since I posted here. Sold my old 08 JKU about two years ago and recently picked up a new to me 09 2 Door 6 speed. Other than aftermarket wheels (stock 32" tires) it's pretty much bone stock and only has 40,000 miles on it.

I have noticed that there is some sort of clunk in the rear end when I take off from stop lights. It's very annoying as I can't duplicate it all the time and it's very random when it happens. It almost feels like when the clunk happens the rear of the Jeep shifts just a little to one side and the odd thing is it never happens when I take off hard, only when I ease the clutch out slowly.

I've crawled under the Jeep and put a big torque wrench on every single bolt and they are all tight. Trackbar, upper and lower control arms and shock mounts, everything is tight. It also doesn't seem to happen in reverse ever.

Any suggestions on what it could be? It's a pretty solid clunk when it happens. Prior to me buying it the previous owner had never taken it off-road.

Thanks for any help.
 

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JKO Dickhead
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Just had the same thing... and everything "appeared tight" diagnosed in about 30 seconds by crawling under neath and (while in park) rocking the rig forward and back as if it was taking off. Both lower control arms were stripped at the shank.

Jam nuts were tight, but must have loosened at some point to allow the shank to move in and out of the arm under acceleration, eventually stripping the entire arm. The shanks fell right out when I took the arms off..

probably something similar or a bad bushing in a control arm I'm guessing
 

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Discussion Starter #3
Just had the same thing... and everything "appeared tight" diagnosed in about 30 seconds by crawling under neath and (while in park) rocking the rig forward and back as if it was taking off. Both lower control arms were stripped at the shank.

Jam nuts were tight, but must have loosened at some point to allow the shank to move in and out of the arm under acceleration, eventually stripping the entire arm. The shanks fell right out when I took the arms off..

probably something similar or a bad bushing in a control arm I'm guessing
Yours are stock control arms? I was thinking it could be a bad bushing, but kind of hard to believe with only 40,000 miles and the girl that owned it before only used it to drive to school and back. I guess stranger things have happened.
 

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Double check your rear pinion. The JK axles use a crush sleeve for pinion bearing preload. The Chrylser 9.25 was notorious for the crush sleeve loosing its preload causing the pinion bearings to loosen up, and cause a "clunk" on take off. Chock the wheels, put the trans in neutral, crawl under and grab the rear pinion yoke. If it has any movement up/down or side to side the crush sleeve has lost its preload. Rotate the yoke clockwise/counter clockwise for excessive backlash that could be an early sign of a crush sleeve issue.
 

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JKO Dickhead
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Yours are stock control arms? I was thinking it could be a bad bushing, but kind of hard to believe with only 40,000 miles and the girl that owned it before only used it to drive to school and back. I guess stranger things have happened.
Sorry.. for some reason assumed you had arms based on your avatar photo. no Aftermarket arms I was referring to the Joint shank in the arm.

Double check your rear pinion. The JK axles use a crush sleeve for pinion bearing preload. The Chrylser 9.25 was notorious for the crush sleeve loosing its preload causing the pinion bearings to loosen up, and cause a "clunk" on take off. Chock the wheels, put the trans in neutral, crawl under and grab the rear pinion yoke. If it has any movement up/down or side to side the crush sleeve has lost its preload. Rotate the yoke clockwise/counter clockwise for excessive backlash that could be an early sign of a crush sleeve issue.
If you have stock arms I bed LedZep is on the money
 

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Discussion Starter #6 (Edited)
I think you're right LedZep. Crawled under there and was able to rotate the pinion a lot and there was a clunk inside. How do I fix this? Damage possible if I continue to drive? Was gonna regear it anyways.

It doesn't move up or down or side to side just has excessive backlash.
 

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I think you're right LedZep. Crawled under there and was able to rotate the pinion a lot and there was a clunk inside. How do I fix this? Damage possible if I continue to drive? Was gonna regear it anyways.

It doesn't move up or down or side to side just has excessive backlash.
Hi svmaniac. Did you resolve the issue with the clunk on moveoff? Was it related to the pinion? I have the same issue and trying to find a solution for it.
 
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