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  1. #1
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    Icon9 Knocking Sound coming from the Rear

    Hey Yall. Just the other day i started to hear this knocking sound coming from the back of the Jeep....

    It only makes the noise at LOW speeds (10-25 MPH) And only when I let off the gas (coasting).

    I can make it go away if I shift into Neutral.

    So this leads me to think there is a problem with the Rear Drive Shaft???

    Or U Joint?...
    Need some help here.. what should I look & check for?

    Thanks guys!

  2. #2
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    Default Re: Knocking Sound coming from the Rear

    Quote Originally Posted by Jdub76 View Post
    Hey Yall. Just the other day i started to hear this knocking sound coming from the back of the Jeep....

    It only makes the noise at LOW speeds (10-25 MPH) And only when I let off the gas (coasting).

    I can make it go away if I shift into Neutral.

    So this leads me to think there is a problem with the Rear Drive Shaft???

    Or U Joint?...
    Need some help here.. what should I look & check for?

    Thanks guys!
    Well I guess it could be a u-joint. Best thing to do would be to get under there and twist the drive shaft by hand and see if you have any play. Get a flashlight so you can look at the u-joint carefully.


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    Default Re: Knocking Sound coming from the Rear

    Does it clunk louder when you first put it in reverse ? If so than a ujoint is very possable. If it only does it in gear when driving it could still be a joint but not likely in my opinion. Little more info please
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    Default Re: Knocking Sound coming from the Rear

    I wouldn't even call the sound a "Klunk" but more of a hard Low Tone Tape that gets faster the faster you drive. But the sound fades away as you get above 25 MPH. and also I just recently installed my 3" Lift.(about 3 weeks ago). could this sound just be Drive Line Vibration due to the different angles???
    I dont know maybe i am being to picky about the noises coming from the Jeep.

    And Remember this is only during Deceleration (slowing down)

    Also I never did recheck Nuts on the U-Bolts on the Leaf Spring. Or the ones for the rear shocks. I guess it wont hurt to check all those?

    I am definitely going to do some inspection with that Drive Shaft... Is any play at all normal while trying to Rotate it by hand? And what about Play moving Back to Front?
    Last edited by Jdub76; 04-10-2012 at 04:31 PM. Reason: Typos

  5. #5
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    Default

    Sounds like the u joints to me,

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    Default Re: Knocking Sound coming from the Rear

    Quote Originally Posted by Jdub76 View Post

    Also I never did recheck Nuts on the U-Bolts on the Leaf Spring. Or the ones for the rear shocks. I guess it wont hurt to check all those?
    You want to check those nuts regardless. I learned that lesson the hard way on my full size Cherokee about two months after I did the lift.
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    Default Re: Knocking Sound coming from the Rear

    Quote Originally Posted by KH96XJ View Post
    You want to check those nuts regardless. I learned that lesson the hard way on my full size Cherokee about two months after I did the lift.
    Oh please tell us the Lesson you learned... What happen?

    I did check everything in the front, and glad I did to. 2 of lower control arms bolts were way loose.

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    Default Re: Knocking Sound coming from the Rear

    Quote Originally Posted by Jdub76 View Post
    Oh please tell us the Lesson you learned... What happen?

    I did check everything in the front, and glad I did to. 2 of lower control arms bolts were way loose.
    Pretty severe case of death wobble. The u-bolts on the front axle had come loose and some of the nuts were about 1/4 inch away from the spring plate. I don't know how I drove it for almost two months before it got that bad and never had one problem till that day. I was only going about 30 mph when it started and I was pretty glad it didn't happen on the hwy and nothing broke. I was paranoid about them after that and would check them once a month for the next 4 months till I was satisfied that I had them torqued correctly.
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    Default Re: Knocking Sound coming from the Rear

    Quote Originally Posted by KH96XJ View Post
    Pretty severe case of death wobble. The u-bolts on the front axle had come loose and some of the nuts were about 1/4 inch away from the spring plate. I don't know how I drove it for almost two months before it got that bad and never had one problem till that day. I was only going about 30 mph when it started and I was pretty glad it didn't happen on the hwy and nothing broke. I was paranoid about them after that and would check them once a month for the next 4 months till I was satisfied that I had them torqued correctly.
    Well you have convinced me to Check and RECheck every thing!

    I am also paranoid about getting the death wobble even tho I have never experienced it, I hear it's Hell to go thru!

    Thanks Man!

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    Thumbs down Re: Knocking Sound coming from the Rear

    Well I checked the Drivshaft & both universal joints, and all of it is really tight no play at all. But I have reason to believe the sound is coming from my Rear wheel Bearings. I think they are totally worn out...

    I have never replaced these before, So this will be a learning experience!!

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    Default Re: Knocking Sound coming from the Rear

    Quote Originally Posted by Jdub76 View Post
    Well I checked the Drivshaft & both universal joints, and all of it is really tight no play at all. But I have reason to believe the sound is coming from my Rear wheel Bearings. I think they are totally worn out...

    I have never replaced these before, So this will be a learning experience!!
    You may need one of those bearing removal tools, at least to get it out easier. I'm wondering if its the ring and pinion now though. Have you checked the fluid in the rear diff?

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    Default Re: Knocking Sound coming from the Rear

    Just throwing this out there if you have a auto it could be a cracked flywheel.
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    Default Re: Knocking Sound coming from the Rear

    I would say try jacking up the rear end, and spinning the wheels by hand see if you can get the sound to happen... if it does, remove the DS and try again, see if you can't figure out where the sound might be coming from that way... If nothing else while you have the rear end up in the air, make sure you are in 2wd, and put it in gear and have someone slow down the tires every so often using the brakes, and see if you can hear where it is coming from while moving around the rear end.... obviously supporting the vehicle with jack stands, and being very careful while moving around...
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    Default Re: Knocking Sound coming from the Rear

    Quote Originally Posted by Mudderoy View Post
    You may need one of those bearing removal tools, at least to get it out easier. I'm wondering if its the ring and pinion now though. Have you checked the fluid in the rear diff?
    I removed the rear wheels & Break Roters, Got the axle spinning pretty good and i couldn't really hear much out of the ordinary. This thing is making me CRAZY

    I guess it's time to pull the Diff Cover and check the Fluid???

    I have a stock Dana 35 in the rear with a rubber cap on it, Can I just pull that cap off and try to top off the Fluid?

    Thanks Mudderoy xjtalk

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    Default Re: Knocking Sound coming from the Rear

    I'd pull the cover, check your gears and such, as well as look at the fluid for metal flakes... and then just replace it with new fluid... Or even better pick up a 29spline Ch.8.25 to swap in!! LOL
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