lower ball joint issue

[dave10450]

I had the passenger side lower ball joint separate from the spindle on my Mk4. Fortunately, I was in a parking lot when it happened. I purchased the car assembled 3 years ago and have driven it about 21,000 miles. I'm struggling to come up with a root cause as to why it happened. The ball joint castle nut backed off, sheared the cotter pin and then eventually fell off allowing the ball joint stud to separate from the spindle.

I've reassembled it replacing the castle nut with a new one and used a stainless steel cotter pin which has a higher shear strength than mild steel which I assume was originally used. I really don't know what else to do other than keep a closer eye on it. The spindles are not Factory Five spindles but I don't know which ones they are. Perhaps this may have something to do with the failure. Any thoughts?179376179375

[Norm B]

Your pictures have me a little confused. The spindle adapter is attached to the spindle in the position required for the 87-93 spindle but you have dual piston calipers that were not normally used until the SN 95 generation. Maybe you have upgraded after market calipers.

Double check the ball joint mounting hole in your spindle for damage. If the ball joint was rattling around loose in a hole it is possible that the hole is deformed and you will not get the tapered ball joint stud to seat correctly.
You may need to put a washer or two under the nut to make sure it is not reaching the unthreaded portion of the ball joint stud before pulling the stud tight into the hole. The hole and the stud should clean and lubricant free before assembly.

HTH
Norm

[rich grsc]

I think Norm is correct that the nut needed a spacer/washer under it. If so, then the nut never torqued down on the spindle and that is why it worked loose. It looks like the threads are damaged on the balljoint, it may need replacing?

[dave10450]

Yes the calipers are Wilwood. Not sure if there was a spacer under the castle nut or not. I'll have to check the drivers side for this. The hole in the spindle looked fine.

I had ordered a new lower control arm from Factory Five but after 2 months and still not having a ship date I decided to reuse the existing control arm. The threads were damaged on the ball joint stud as you noticed Rich and I rethreaded them using a die, and when I reassembled everything I did use a spacer, approx 1/4" thick. I couldn't use a torque wrench due to space limitations but I did crank it down pretty good.

[rich grsc]

The ball joints are replaceable, but if the threads cleaned up ok then reusing it was ok.

[Norm B]

You do not need a new lower control arm. The ball joint is pressed in and is replaceable. I believe it is the same part as on the 87-93 Mustang. If I am wrong someone will correct me soon.��

Norm

PS Rich and I must have been typing at the same time

[edwardb]

Before reading the other responses, I was going to say the same thing... Likely the castle nut was never torqued properly. Or ran out of threads and needed a spacer to properly engage the taper between ball joint stud and the spindle. The cotter pin is a safety device for obvious reasons. But installed properly, the nut shouldn't loosen enough to shear it.

[Mike.Bray]

A taper less than 7 degrees is self-locking and ball joints are typically around 4-5 degrees taper. This taper carries the majority of the load (weight of the car) which is why it is critical that the male & female be absolutely clean and perfect. Once the nut cinches it up it should be locked until you literally drive them apart. I agree with the above comments, either the tapered bore was dirty and/or damaged or the spacer was missing and the nut/taper never got tight. The nut on its own cannot support the weight of the car.

[BradCraig]

This likely took a while to fail, and why it is so important to perform a yearly nut and bolt inspection. Get the car in the air with all four wheels off and inspect EVERYTHING!, especially if you didn't build it. It may save your life.

[Ford & Jeep Fan]

the inside of wheel has been rubbing on something. during/after this event? if not related it still needs looked into.

[dave10450]

Appreciate the replies. Yes the control arm did rub against the inside of the wheel for a brief time (100' or so) at low speed. I did look at it closely and the damage is minimal.
Agree on inspecting everything that I can. The car is up on jack stands and I'll be checking fastener tightness on those that are accessible, and will also put a paint mark on them.

[seagull81]

If you need to add a washer or two, be sure the inside diameter is large enough to go over the tapered part of the ball joint.