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Unread 05-09-2012, 09:06 PM   #1
goatmurray
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Front end thumping at low speed

My jeep has recently started making a thumping/banging sound in the front end. It's a repeating sound, and the faster the wheels are spinning, the faster the banging is. At first I thought it was a u-joint or the gears in the differential, but I'm no mechanic. Sounds something like that, though.

It likes to do it when I'm creeping through a parking lot either coasting, stopping, or on the gas very lightly. Only does it sometimes, seems like more often when it's warmed up, but I don't stop much until after its warmed up anyway...

I noticed it started right around the time I changed my front diff fluid. I was careful to keep it clean inside and put 75-90 in the first time with mopar friction modifier. Night before last I changed it again to 90-140 to see if that would quiet it down. No effect.

It's a |6 automatic with selectrac.

It's louder and more likely to happen if my sway bar is disconnected.

Pretty much all the bushings on the RE 4.5 lift are shot. Maybe that's it?

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Unread 05-10-2012, 05:01 PM   #2
goatmurray
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Nobody?
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Unread 05-10-2012, 05:12 PM   #3
PolkaPower
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Bad bushings can cause thumping. You don't need friction modifier in the front.
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Originally Posted by jabba974
"And yes, there is always a torque spec...but its not necessary...and takes way to much time...."
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Unread 05-10-2012, 09:19 PM   #4
westcoastvibes
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I had all kinds of thumping and clunking, after a thorough looking I ended up replacing both lower control arms, both sway bar end links (not the bushings but the whole dog bone assembly) and the shocks. turns out the PO replaced the shocks and put sub par bolts that were undersized causing the shocks to clunk, the control arm bushings were so loose that they just fell out when the bolts were removed and the sway bar end links had no bushing left in them at all. It took me a while but the clunks and bumps are all gone now.
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Unread 05-11-2012, 12:49 AM   #5
PolkaPower
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Kinda weird that you have a4.5" lift and can't figure out if it's the worn out control arm bushings or not. It would seem to me like you have had it long enough that you would know better that if you have worn bushing, they need replacing.
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Originally Posted by jabba974
"And yes, there is always a torque spec...but its not necessary...and takes way to much time...."
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Unread 05-14-2012, 08:56 PM   #6
goatmurray
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Oh I definately need new bushings... That need has been identified from day -1.
And it makes a thumping, thunking, creaking sound every time anybody looks at it, but this thumping isnt just a solitary thump when I accelerate or hit the brakes.

It almost sounds like a U-joint is really sloppy and is being turned at excessive angles, but it's not the front driveline from what I can tell.
My brother said it sounds like a spider gear keeps trying to grab, but let's go. (IDK)

What it REALLY sounds like is a fender rubbing on tire tread, but there's no way that's what it is. And it sounds metal-on-metal. And it's not quite as fast as fender on tread.

Assuming the previous owner had a LSD installed, and I didnt put friction modifier in it, what would it sound like?
I'm pretty sure the rear diff is limited slip... not positive about the front.
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Unread 05-14-2012, 09:09 PM   #7
TheHalfWit
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What'd you see when you dropped the diff cover?

If you saw this then its open and doesn't require anything special.

That aside, fix what you know is broke i.e. the control arm bushings, than try troubleshooting it. Personally I just had one look at my jeeps 17 year old, mostly original suspension and ripped everything but the ball joints out and rebuilt it figuring that if the control arm bushings were dry rotted, every other bit of rubber down there was in the same condition and needed replacing to be free of clunks/squeaks.

Speed based though I'd try wiggling each of the U-joints, maybe see if all your caliper bolts are snug (funny as that sounds.)
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Unread 05-17-2012, 08:37 PM   #8
goatmurray
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I didnt see that^.
I don't recall seeing a differential case like that.
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Unread 05-17-2012, 08:44 PM   #9
jtackerman28
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Quote:
Originally Posted by goatmurray
I didnt see that^.
I don't recall seeing a differential case like that.
Front axle u joint. Not drive shafts. I bet they are about to fall out.
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Unread 05-30-2012, 01:33 PM   #10
goatmurray
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My Jeep has stopped making the sound...

U-joints seem fine, though.
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Unread 02-17-2013, 01:51 PM   #11
goatmurray
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Dunno how I missed it, but you were right. U-joints were about to fall out.
I should make a video, it'd blow your mind.
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Unread 02-17-2013, 04:33 PM   #12
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Engine mounts? Does the the "thunk" occur during acceleration and just after braking?

Hunter
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Unread 02-17-2013, 05:34 PM   #13
goatmurray
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Thanks, but I resolved it. It was the axle U-joints. They were long gone. Like I said, I don't know how I missed it. Thanks for the responses!

On the subject of thumps, though, does anyone know where could get some rear lower control arms for a RE 4.5" long arm kit? Mine got bashed open by the PO. I heard RE went out of business??
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Unread 02-17-2013, 06:07 PM   #14
PolkaPower
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You mean these guys http://www.rubiconexpress.com/

They did for a while but they are back.
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Originally Posted by jabba974
"And yes, there is always a torque spec...but its not necessary...and takes way to much time...."
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Unread 02-18-2013, 07:14 PM   #15
goatmurray
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Hmmm Son of a gun.

Thanks!
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