Ball Joint, Dissected

[Mxfrank]

And the saga continues. I was thinking about installing zerks in my balljoints (sounds painful), so I began by disassembling a scrap example.

The balljoint is pretty simple. The shell and ball are the major components. The ball sits in a nylon grease cup. Below the grease cup is a rubber spacer, and then a steel cap. The cap is crimped into place. The crimps are super heavy duty, but no match for a cold chisel and a 3lb hammer.

My conclusion: it's not possible to install a zerk. Drilling through the steel bottom cap is simple enough, and the nylon cup has a hole and grease grooves which should make it simple. But the dense rubber plug seals the hole in the nylon cup. Unless you somehow manage to clear out a donut hole, it's not going to work.

[bolzano]

Well done. Was there still grease in the joint? So when a ball joint wears and gets loose, which part wears? The steel, nylon cup, black rubber plug, or something else.

[Mxfrank]

The boot had failed, allowing water into the joint. The ball and shell were corroded.

[Mike D]

Adding a zerk fitting would DECREASE the life of the ball joint. Any metal/grit particles introduced into the nylon wear pocket by way of the grease will act as an abrasive.

The possibility of incompatibility of the grease and the nylon is also to be taken into consideration.

The old metal to metal joints required the additional greasing, not so the modern ones.

[Turbo190D]

Interesting. I noticed when I was replacing the control arms that the ball joints didn't have zerks. Thought that was odd, since my 86.5 hardbody has zerks on its ball joints. Thanks for taking the time to dissect them.

[Mxfrank]

Originally Posted by Mike D

Adding a zerk fitting would DECREASE the life of the ball joint. Any metal/grit particles introduced into the nylon wear pocket by way of the grease will act as an abrasive.

The possibility of incompatibility of the grease and the nylon is also to be taken into consideration.

The old metal to metal joints required the additional greasing, not so the modern ones.

Attachment 143986

And yet, the nylon cup has a grease port and distribution grooves. The ball impinges on the top of the steel shell, so the bearing surface is more than nylon. It's hard to say what the cr_p in there originally was, but I'm pretty sure it was contaminated grease.

[97 SL320]

The rubber spacer is actually a spring. This keeps tension on the joint as it wears. Once the joint wears enough, the rubber spring is fully expanded and can't take up any more clearance.

Nylon can absorb water and oil causing it to swell. Probably not much of a consideration in this application but it is a consideration when nylon is used as a bushing as swelling will bind the shaft.

An end mill run through the end cap while using a vacuum to pull chips would produce a grease channel. Given the ball has a flat spot where one would be drilling, there won't be any damage to the ball.

For 100 % completeness a new ball joint would need to be taken apart as details may have changed. ( thought I doubt it )