Ball Joint Warning

[tmontague]

I figured it was worth mentioning my recent experience with the ball joints on my Yaris to save someone guessing down the road. Long storey short after I installed my transmission built by Tom w/ the reduced final drive and clutch type LSD, I had some clunks and noises that weren't there before. This is not really a surprise as clutch type LSD are known to be noisy.

Anyways, after installing my custom rate coil overs I noticed my steering wheel was off center and I had a loud clunk sometimes when going in and out of a driveway. This made no sense as I didn't mess with the tie rods and the ride height was essentially the same. What was more strange was that the steering wheel angle got progressively worse a week later, then better and then worse. Change like this typically signals warn suspension parts. Every single part is brand new in my suspension except for the ball joints. I checked for tire play at the 12 and 6 o clock positions and there was none, everything felt rock solid.

I got a race alignment and re centred the wheel, a week later same issue. I took it back to the alignment shop and the alignment was bang on perfect. The mechanic told me to change out my ball joints as he said he had seen it before. A week later while driving it and waiting for the ball joints to show up the clunk I would hear made more sense that it was the ball joints. It would happens when torque direction was changed on the wheel - entering or exciting driveway curbs at a sharp wheel angle, coming to a stop etc.

The mechanic explained that what happens is a small part of the nylon cup that the ball sits in becomes worn. In a high torque/power front wheel drive car with very tight suspension parts the nylon cup will actually rotate during hard corners which moves the pocket that is worn. This small tolerance causes large changes in the steering due to it being located on the outer most part of the suspension control arm. The reason the wheel feels solid is the worn part is so small and sometimes its in a position that you cannot feel by using your hands to move the wheel.

In a stock car the soft suspension and rubber bushings will hide the mildly worn ball joint. But in a track set up car with poly bushings and coil overs at triple the spring rates of factory specs plus running r40 compound tires, this shows up at a problem.

I replaced both ball joints today w/ Moog parts that comes with a grease fitting. The passenger side was still tight and solid but the drivers side was very loose. This alone isn't typically a problem but when you pushed the joint in and out there was a very small amount of play that you could barely detect, but it was there.

New ball joints in and the clunk sounds is gone. Steering wheel is slightly cocked to the right so I'll have to go back for an alignment again to correct the toe.

Keep this in mind if this ever happens to your steering/alignment and you are running stiffer suspension components. I had 215k km on my original ball joints, not too bad considering the roads around here suck.

As a side, when replacing your ball joints keep in mind that there is a snap ring located under the boot on the oem ball joints. Remove that before you press out the joints.