Help! Feels Like There Is An Earthquake Under My Jeep!!! - JeepForum.com

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post #1 of 18 Old 11-30-2009, 05:46 PM Thread Starter
cracked91
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Help! Feels Like There Is An Earthquake Under My Jeep!!!

So 2nd time this has happened, I start driving and when I hit about 30 the whole world goes to hell. Something goes pop and the entire truck starts shaking violently like there is an 800 pound monkey jumping up and down on the nerf bar. I can see absolutley nothing wrong, the only thing I could think of it being would be maybe the gears in my front axle?? Any help would be greatly appreciated.

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post #2 of 18 Old 11-30-2009, 06:11 PM
-AC-
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Sorry, but not enough info. Does it matter what gear your in? Does it go away as you decelerate or do you need to come to a stop? Can you drive through it and have it smooth back out? General condition of the running gear? Tires? Your profile says you need to replace the front axel. Is there a known issue? Need more input.

Good Luck

"Damn Everything But The Circus..." e.e.c.
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post #3 of 18 Old 11-30-2009, 07:10 PM Thread Starter
cracked91
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There is a known issue with the gears in the front axle, but it only comes up in 4 wheel drive. I have never tried to drive it through, and it does not matter what gear. It only stops when I stop. I had a shock mount snap on the drivers side, so I just took the shock off. I plan on replacing it right away, but one missing shock could not cause that could it?
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post #4 of 18 Old 11-30-2009, 07:23 PM
-AC-
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Uh, Yeah. I'd bet $50 that you've already found your problem. With no damping device (shock absorber) there is nothing to stop the numerous forces at work while driving from oscillating and compounding. I would suggest a $20 cheapo shock as a bare minimum before driving it again. As, I think it was JeepHammer, once said "The life you save may be mine!"...

Not that I find myself in Arizona very often.

"Damn Everything But The Circus..." e.e.c.
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post #5 of 18 Old 11-30-2009, 07:26 PM
bogiemj
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Just a thought but i would also check the track bar
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post #6 of 18 Old 11-30-2009, 07:36 PM
rixcj
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How's your steering dampener...a good one can help prevent the dreaded "death wobble".

Rich

'79 CJ5, AMC 360, t-18/d20 twin stick, dana 30/amc20(Mosers), Edelbrock Performer intake, Holley 600, ps/pb, DUI HEI, 'glass tub/1pc. tilt nose, 33x12.50 BFG AT's.

There's a fine line between "hobby" and "mental illness".
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post #7 of 18 Old 11-30-2009, 08:21 PM
jeepdaddy2000
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Sounds like the dreaded "death wobble". This is caused by a number of things.
Bad caster angle
Extended/bad shackles, worn bushings, loose wheel bearings, bad ball joints, bent frame, bad/bent springs.etc......
The bottom line is you will need to start by doing a through inspection of the front end components.This includes the "wiggle test" where you have a buddy move the wheel back and forth while observing for any front end movement. You will want to replace, fix, tighten and repair any issues you find (you should be doing this anyway) When all is said and done any you are confident that all the components are good, you will need to check the caster angle. This can be done professionally or you can purchase a relatively inexpensive tool to check it yourself. You can then purchase the correct angled shims to correct any issues you find.
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post #8 of 18 Old 12-01-2009, 08:11 AM
Gunga
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Quote:
Originally Posted by bogiemj View Post
Just a thought but i would also check the track bar
Track bar??

'78 CJ-7, 401 w/ headers, T-18, 35" muds, 4" lift, MSD ignition box, locked diffs.
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post #9 of 18 Old 12-01-2009, 08:29 AM
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Quote:
Originally Posted by jeepdaddy2000 View Post
Sounds like the dreaded "death wobble". This is caused by a number of things.
Bad caster angle
Extended/bad shackles, worn bushings, loose wheel bearings, bad ball joints, bent frame, bad/bent springs.etc......
The bottom line is you will need to start by doing a through inspection of the front end components.This includes the "wiggle test" where you have a buddy move the wheel back and forth while observing for any front end movement. You will want to replace, fix, tighten and repair any issues you find (you should be doing this anyway) When all is said and done any you are confident that all the components are good, you will need to check the caster angle. This can be done professionally or you can purchase a relatively inexpensive tool to check it yourself. You can then purchase the correct angled shims to correct any issues you find.

Im surprised you took the time to list it all again.

But yes, this is exactly what you need to do.

Unless you have a lift thats not properly set up then most likely you have a part failure or a wallowed out hole on the track bar axle bracket or a tire problem.
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post #10 of 18 Old 12-01-2009, 07:35 PM
gojeepin
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Bad caster angle doesn't cause wobble... it causes wander.
Leaf spring vehicles don't need and CJs didn't come with track bars (YJ Wranglers did).

Does the wobble start when you hit a bump?

Vibration? Bump steer? Wandering? Read the article (sticky) on Steering, suspension, and driveline.
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post #11 of 18 Old 12-01-2009, 08:08 PM
ZJFABN
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Quote:
Originally Posted by gojeepin View Post
Bad caster angle doesn't cause wobble... it causes wander.
Leaf spring vehicles don't need and CJs didn't come with track bars (YJ Wranglers did).

Does the wobble start when you hit a bump?
oops. I need to look at what their driving more. I do that all the time
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post #12 of 18 Old 12-01-2009, 08:31 PM
jeepdaddy2000
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Quote:
Originally Posted by gojeepin View Post
Bad caster angle doesn't cause wobble... it causes wander.
Leaf spring vehicles don't need and CJs didn't come with track bars (YJ Wranglers did).

Does the wobble start when you hit a bump?
Bad caster can indeed indeed cause wobble.
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post #13 of 18 Old 12-01-2009, 08:37 PM
-AC-
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You know, maybe I'm missing something, and I have to admit that I haven't spent much time drivng around a short wheel-based vehicle without a front shock, but I still have to think that until he gets a shock on the one front corner none of this is going to get any better.

Um, Hello? No front shock here!!! Am I missing something?

"Damn Everything But The Circus..." e.e.c.
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post #14 of 18 Old 12-01-2009, 09:23 PM
godfather901
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Had the EXACT problem - turned out my rear u-joint (which looked fine) had eaten all it's little internal bearings and was using the cap as a horrible stand in for them - 30 min fix. I'm sure checking all the rest of the front end is a great idea too, but after what you've described change the u-joints.

1979 CJ5 304, 3spd USAF 32 Combat Comm "Anytime, Anywhere"
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post #15 of 18 Old 12-02-2009, 06:18 PM
gojeepin
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Quote:
Originally Posted by jeepdaddy2000 View Post
Bad caster can indeed indeed cause wobble.
Always ready to learn. How does it cause the wobble?

Vibration? Bump steer? Wandering? Read the article (sticky) on Steering, suspension, and driveline.
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