How to Diagnose a Bad Ball Joint

Hi, I’m Mike from 1A Auto. We’ve been selling auto parts for over 30 years!

What's up, guys? I'm Andy 1A Auto. In this video, I'm going to show you how to properly check the front lower ball joints with a dial indicator. If you need any parts for your vehicle, click the link in the description and head over to 1AAuto.com.

What we want to measure today is the play in the front lower ball joints. Basically, the distance between here and here, the movement when the knuckle goes up and down. This right here happens to be a load carrying ball joint. What that means is the weight of the vehicle is on this control arm, and it pushes down on the ball joint, and that is what holds the vehicle right there.

So, to test this, this is a little bit different than testing some other types of ball joints. To check this lower ball joint, we actually need to raise the suspension a little bit. We need to take the weight off that lower ball joint, because right now, the spring is pushing down on the lower control arm, which is pushing it down so it's nice and tight against that knuckle. So when we raise it up, that knuckle will just be suspended, then we can check the play. We'll take a pry bar and stick it underneath the tire.

One of the ways you can tell whether you have a load carrying ball joint or a non-load carrying ball joint is where the spring is located. If the spring is located in a position where it attaches to the lower control arm, that's a load carrying ball joint. If the spring is located where it's attached to the top of the knuckle, then the lower ball joint is not going to be a load carrying ball joint. If you have torsion bars and it connects to the lower control arm, that's going to be a load carrying ball joint. Wherever the spring is located, that's how you can tell whether it's load carrying or non-load carrying.

As you can see on this vehicle, this has a lower ball joint that's not connected to the spring. There's no support on this lower control arm. The strut is what is connected to the spring, and that connects to the upper part of the knuckle, so this is not a load carrying ball joint. So, the obvious reasons why you'd replace the ball joint is if the boot's ripped or if it's binding up, if it's squeaking when you turn left and right. We're going to check the tolerance. Just because there is play in this ball joint doesn't mean it's bad. You're actually allowed 20 thousandths of play, up and down vertical movement. If you have a lot of side-to-side movement, then it needs to be replaced as well.

But we're going to check it with this tool. What we're going to do is we're going to hook this, this locking pliers side to the lower control arm here. Now we're going to take this gauge and we're going to put this on the knuckle side, right here. There's a lot of adjustments with this tool. So it's easy to lift the vehicle and get this tool set up first, and then I can lock this down right here.

You want to make sure this stabilizes. You might have to tighten it up a little bit. Tighten that up. Make sure the gauge isn't touching the tire. That looks pretty good. Now we're going to lower the vehicle, and then we're going to support the lower control arm.

So now I'm going to take a floor jack. I'm going to try to get as far out on the lower control arm as possible, without hitting the tool. You might have to adjust the tool a little bit. Okay, I just adjusted the tool so it's out of the way of my floor jack. So now I'm going to raise the front suspension. Now, it says to raise the lower control arm about an inch, so you want to make sure, make sure you have about an inch of clearance underneath the tire.

All right, now I'm just going to zero the gauge before I pry underneath there. That's pretty close. Whoops. It's pretty sensitive, so every time you touch it, it does move a little bit. There we go. All right, that's pretty close.

Right, now I'm going to put the pry bar underneath the tire, and I'm just going to raise up on the tire and let it down. I can actually feel a lot of movement as I do this. And you can have a partner do this while someone else checks the gauge. As you can see, the gauge is moving almost 50 thousandths, which our tolerance is 20 thousandths, so this is 30 thousandths over spec. So this ball joint would need to be replaced at this time.

So this being 50 thousandths over, obviously we would want to replace the ball joint at this time, but you want to keep in mind that if you had a ball joint and it was only moving about that much, 10 thousandths, then the ball joint would be fine. There'd be nothing wrong with the ball joint. It is still good. There's no need to replace it.
This happens to be a 2009 Chevy Suburban. Other vehicles may have a similar procedure. You're going to want to check a repair manual for tolerances. I hope this video helped you out.

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