Is my ball joint shot, or is this normal play??

[ChrisD]

Would you consider this ball joint shot or normal play? The bottom ball joint has zero play, only the top.

[Kurt]

Normal
Looks good to me. It's designed to have some vertical movement.
Just a long as it freely rotates and has no side to side movement your good.

(The heavy breathing in the video was funky tho! )

[Frank]

Kurt : You can have vertical movement and your good with that ? I thought any movement vert or hor would say wear and how much is a matter of specs. on when to change . FjR68

[ZAEDOCK]

The joints could be replaced. I wouldn't say that amount of play is excessive though. Typically, on a rear wheel drive SLA suspension, the bottom joint is a "loaded" joint and the top a "follower". You can have some top play and be OK, but the way the Jeep spindle fits on the knuckle, the only way you would see movement of the top balljoint, would be if there was play in the bottom.

[Kurt]

Kurt : You can have vertical movement and your good with that ? I thought any movement vert or hor would say wear and how much is a matter of specs. on when to change . FjR68

Yes.
The lower ball joint is the one that actally supports the the axle "C" and carries all the vertical load (weight).
The upper ball joint is there to maintain the steering knuckle in a vertical position and provide a pivot point for the top of the knuckle. It does not provide vertical load support. If much vertical load was put on it the upper ball joint would pop out the top of the "C". It's pressed in from the top of the "C" and not the bottom as the lower joint is.
Due to minor differences in the machining of the steering knuckle, tapers, ball joints and the "C" the upper ball joint has to have a bit of vertical movement designed into it to compensate for the minor differences in machining and movement.
If the ball joints were machined such that neither allowed any vertical movement the dimensions of all the components would have to all be "perfect" dimensionally otherwise the knuckle would bind up and not pivot properly.
If you examine a new upper ball joint you will see that the shaft does move in and out a bit.
It quite apparent as you assemble the knuckle onto the new ball joints. If you first tighten up the nut securing the upper ball joint first you'll usually see some of the upper ball joint shaft partially exposed due to the weight of the knuckle hanging on the upper ball joint. As you screw on and tighten the lower ball joint nut it forces the steering knuckle up as the lower tapers seat and inturn push's the upper ball joint shaft updards until the lower ball joint taper is fully seated.

I do agree that the lower ball joint shouldn't have any vertical play in it.

The upper ball joint in a Jeep is the "follower" type (not loaded) shown on the left below.

There is actually a spring inside under the cap for the movement.



All sorts of gory details here for further nightime reading http://www.aa1car.com/library/ball_joints.htm

[ZAEDOCK]

I do agree that the lower ball joint shouldn't have any vertical play in it.

We also agree on the ball joint types. However, unlike a short/long arm suspension, on a fixed spindle and knuckle setup, if you can see verticle movement in the upper, then there is verticle movement in the lower. They should be considered for replacement if the play is excessive, IMO.

I am fortunate that both upper and lower ball joints in my YJ's front axle are load bearing.

[Frank]

Thanks for the update ! Both of my joints go into the -C- from the bottom. There is no room for the upper grease fitting once the axle is installed. Its a pain but twice a year I pull em and give em a shot . In the uppers I also have a little threaded sleeve that gets tightened first setting preload , and they have offset ones to align the vertical access (camber) . I guess its a matter of OLD vs. NEW SKOOL ! FjR68

[Kurt]

I guess its a matter of OLD vs. NEW SKOOL ! FjR68

LOL!

TJ Upper Ball Joint Cut away to illustrate normal "follower" vertical operation.

[youtube][/youtube]

Another video with the cone retaining spring and top removed to see better.
[youtube][/youtube]

Only the thin metal top with the zerk in it prevent it from popping out the top of the joint.

The upper joint consists a slit plastic cone and spring assembly which self adjusts. As the inside of the cone wears from shaft movement the spring forces the cone down into the ball joint housing to take up the slack between the inside of the plastic cone and the shaft.

Picture of tapered plastic cone and shaft.

[Frank]

What will they think up next ! Plastic ball joints, gotta get me some. That just blows me away that a critical part like that can deal with normal stuff vs. what we do. FjR68