Ball joints: How can I tell if they are bad?


Vtx531

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I jacked up my Jeep under the front axle. I stuck a pry bar under the tire and I’m getting quite a lot of up/down movement on both sides. Noticeably more on the passenger side. .090” pass .035” driver. Visible movement with a noticeable clunk when going up/down.

So I’m thinking “Great! I found my wobble/shimmy/vibration problem!”

I did a little research online before I decide to order new ball joints and it looks like that is NOT the sign of a bad ball joint. Then I see there are different types of ball joints- loaded and unloaded. Now I’m confused.

What is the proper way to check for bad ball joints? I saw a thread where Mr. Blaine checks the upper joint for lateral play and replaces both upper and lower if the upper has lateral play? Am I understanding that correctly?

I put a dial indicator on the edge of the rim at the top 12 oclock position and I’m getting about .060” lateral play on the passenger side and .040” on the driver side when I push/pull the top of the tire with the ball joints unloaded/axle jacked up/tire off the ground. No visible movement to the naked eye though and no clunking, unlike the up/down movement.

Is that the acceptable way to check the ball joints? If not, how do you do it? What, if any lateral play is acceptable? I suppose it could be the wheel bearings, or rim deflection contributing to the lateral play they way I tested it so I haven’t necessarily isolated the ball joint as the sole factor using that method. Maybe stick the indicator on the inside of the knuckle?

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RMETeeJay

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I get into a position where I can watch the joint as I use a pry bar under the tire. You shouldn't see any movement in the joint as you apply upward pressure.
 
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HYRYSC

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When you apply the pressure, I would watch where the play is coming from. You should be able to see if the balljoints are allowing that movement however with you talking about lateral movement, that would certainly suggest unit bearing issues.
 
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Vtx531

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I get into a position where I can watch the joint as I use a pry bar under the tire. You shouldn't see any movement in the joint as you apply upward pressure.
I see a lot of movement in the joint up and down when I do this and I can hear a clunk.

When you apply the pressure, I would watch where the play is coming from. You should be able to see if the balljoints are allowing that movement however with you talking about lateral movement, that would certainly suggest unit bearing issues.
I don’t think the play is coming from the ball joint and maybe not bearing either. The up/down definitely is but the in/out feels more like applying a pressure than looseness/play. For instance, if I apply a little bit of pressure back and forth, it will go +- .010. If I press a little harder in out, it will go +-.020. Press a little harder +-.030 which is about as much as I can get but it seems like the ball joints themselves are tight in this direction. And no knocking or clunking in this direction.
 

Rubicon John

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If I suspected movement I would grab a friend and mimic the condition while the other person studies the suspension with a close eye. Even if it takes 5 minutes of ongoing rocking that wheel around. You should be able to spot it with enough repetitiveness.
 
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WallyWest

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BTT Anyone else have anything to add about the up/down ball joint movement being okay or not? No movement is acceptable?

Seconded.

I swear I read something from Blaine about how the TJ ball joint design moves a bit when you pry under the tire with it jacked up in the air. And that it's perfectly normal. But that's just a fuzzy memory.
 

mrblaine

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Seconded.

I swear I read something from Blaine about how the TJ ball joint design moves a bit when you pry under the tire with it jacked up in the air. And that it's perfectly normal. But that's just a fuzzy memory.
Roughly 1/16" vertical play is allowable. No lateral movement of the upper is allowable. I always knew the upper tolerance, I finally got in touch with a mechanic who has access to a database for vertical. If we replaced ball joints at the lower when there is any vertical, we'd be swapping them out every 5000 miles.
 
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Vtx531

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1/16” is .0625” so my passenger side is bad at .090” vertical and my driver side is good at .035”

Would this contribute to tire related vibration if there is no lateral movement in the upper? Just vertical play.

Are ball joints something that should be replaced on both sides at the same time or just replace the offending side?
 

mrblaine

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1/16” is .0625” so my passenger side is bad at .090” vertical and my driver side is good at .035”

Would this contribute to tire related vibration if there is no lateral movement in the upper? Just vertical play.

Are ball joints something that should be replaced on both sides at the same time or just replace the offending side?
If we find one bad out of the 4, we replace them all.