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Unread 11-03-2011, 09:25 AM   #1
00JGC00
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Loud Front End Knock - goes away when brake is applied.

Was on the way to work this morning and just before I got there, a slight knocking sound started to creep up. It started really quiet and then just got louder and louder until it became so loud I had to pull over and see what the heck it was. I immediately assumed the front drive shaft because the knocking speed seemed tied to the vehicle speed. Strange thing was that when I applied the brake, the knocking stopped. It only knocked if I was applying throttle or coasting. Anyway, I got under the Jeep and everything looked totally fine. I had my wife coast along in the Jeep while I listened oustide the vehicle and it sounds like it's coming from the driver front wheel (but because of how knocks can vibrate through metal, I could see it coming from anywhere on the front axle really - the driver side is just where I heard it best).
Anyway, I had to leave the Jeep there and borrow a friend's car to get to work so that's all the info I have at this point. On my lunch I'm gonna go try and take the tire off and see if I can't figure out what's going on.

I know this is very limited info, but any clue as to what that might be? I thought the brake application making the sound stop was very odd and might provide a clue?

Thanks for the help

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Unread 11-03-2011, 09:41 AM   #2
smunns
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I don't know if this could be it or not, but I had the top bolt on one of my shocks come loose on the way to Moab this year and it was knocking in a similar fashion. It started out minor and then got a lot worse as the bolt loosened more.
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Unread 11-03-2011, 09:50 AM   #3
00JGC00
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I would've never thought of something like that. I will check that out as soon as I get there - thanks for the thought man.

I'm gonna puke if it's something with the front diff. That would mean both diffs took a crap this year.
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Unread 11-03-2011, 10:02 AM   #4
smunns
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I would check both ends of each shock, all front control arm bolts, track bar bolts, all tie rod ends (I had one come loose recently), disconnects, driveshaft, lug nuts, wheel bearings, and ball joints. That would cover about everything besides the axle itself.
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Unread 11-03-2011, 10:08 AM   #5
Rocklobster
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Maybe a wheel bearing ?
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Unread 11-03-2011, 10:19 AM   #6
00JGC00
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Quote:
Originally Posted by smunns View Post
I would check both ends of each shock, all front control arm bolts, track bar bolts, all tie rod ends (I had one come loose recently), disconnects, driveshaft, lug nuts, wheel bearings, and ball joints. That would cover about everything besides the axle itself.
Will do. I'll probably be heading over there in about an hour. Thanks again man - very appreciated.

I had something kind of similar happen on the freeway once (not near this loud though) and it was the jam nut on my JKS TB that came loose. I was really hoping to see it loose again but it's still tight.

Dumb question - is there an elegant way to tell if your ball joints are bad?

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Originally Posted by Rocklobster View Post
Maybe a wheel bearing ?
Hopefully it's nothing more than that at least. A wheel bearing I could live with.
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Unread 11-03-2011, 10:23 AM   #7
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It's may be caliper or caliper bracket related. Like a bolt was lost and it's banging around now. I say this bc u said it disappears when u brake.

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Unread 11-03-2011, 10:26 AM   #8
00JGC00
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Yeah, that'd be nice and simple too.

The other thing that I find weird is that it seems to be tied to axle revolutions. Like it will knock once for every time the axle rotates a full 360 degrees. The faster the axle goes the faster the knock, but it's very steady and constant. If it was a shock bolt or a caliper, etc, I would think it would be more sporadic, but who knows.
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Unread 11-03-2011, 11:39 AM   #9
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Hmm... does sound like a loose caliper - been doing brakes recently??
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Unread 11-03-2011, 11:45 AM   #10
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Well i replaced the axle shaft like a month or two ago and today is the first time I've heard any knocks or anything. Since then I haven't touched it. I went and did some wheeling like two weeks ago and had no issues.
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Unread 11-03-2011, 11:52 AM   #11
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Alright, I'm headed over to tear into it. Wish me luck and thanks for the help. I'll post back with what we find.
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Unread 11-03-2011, 02:43 PM   #12
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It was just loose lugs!! I usually torque them to 110 lbs, is that not enough??
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Unread 11-03-2011, 03:47 PM   #13
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You need to re-check them on aluminum wheels after about 25-50 miles or so.
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Unread 11-03-2011, 04:00 PM   #14
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Oooo, good point. I never thought about that. Well good thing no one died! haha
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