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Old 10-14-2011, 04:36 PM   #1
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annoying knocking sound underneath

When I drive my jeep, there is a knocking sound coming from the underneath front of it towards the front. It only does it when moving, beit under load or not, and isn't really speed dependent.

I went underneath and tried to see what is loose. I found that my front drive shaft rocks easily side to side, but is tight forward and back. When I rock it it makes a sound similar to what I hear when driving. I took the jeep out and shifted it into 4x4 and the sound stopped so I guess it's related to the front driveshaft movement.

What could be wrong that causes that sound/movement?

Thanks

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Old 10-14-2011, 05:06 PM   #2
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motor/transmission mounts would be a start if the u-joints are good.

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Old 10-14-2011, 05:23 PM   #3
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but why would the driveshaft make that noise when I move it by hand if it was a mount?
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Old 10-14-2011, 06:40 PM   #4
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to make myself clear, I can replicate the noise when I rotate the shaft side to side, not that it physically moves side to side in the vehicle. thanks
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Old 10-15-2011, 02:34 AM   #5
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Sounds like the front axle u joint to me. I had the same symptoms a couple months ago. Its a cheap part, if that's the problem.
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Old 10-15-2011, 08:05 AM   #6
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yeah, it would be great if it's just a ujoint
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Old 10-15-2011, 08:07 AM   #7
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is the slip joint wobbley?
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Old 10-15-2011, 10:41 AM   #8
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From what I'm understanding Raycer to say, something has slack in it when rotating the drive shaft back ans froth, like ring and pinion.
Raycer is this what your meaning.\? sorry just trying to understand, thanks.
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Old 10-15-2011, 12:04 PM   #9
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Yeah, like there is some slack in the transfer case. I know the shaft isn't engaged in 4x4 mode, but is seems to rock too much while driving and is audible. When I engage 4wd or even just rotate the shaft the whole 360* around, it doesn't do it.

99Jeeper: the slip joint is firm.

Thanks for all the replies everyone, I appreciate the help
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Old 10-15-2011, 12:53 PM   #10
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I'd pull the cover off the front axle and have a look, new oil and a gasket is all it cost.
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Old 10-16-2011, 01:57 PM   #11
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I think I may know what's wrong. U went underneath the jeep and tried to move the tcase/tranny. I realized I can move it a little bit; not more than like 1/8 of an inch but when I do so it makes a sound similar to what I hear when driving so think the tranny mount is messed up. I guess I have to drop the skid plate to change it right?
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Old 10-17-2011, 12:50 PM   #12
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So is there a way to change the tranny mount without removing the cross member?

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