Here are the old spherical bearings from my Elephant Racing Rear Trailing Arm Monoballs.
The left lasted 45,000 miles, the right just came out yesterday after 50,000 miles.
Seems the ball stays pretty tight in the outer race until the chrome plating is defeated. Then the wear rate increases exponentially. You can see how deep the grooves are. The one on the right was fine at 45,000 miles, and sometime this fall it started to fail. Maybe noticed it in November, definitely toast in December
This makes for very erratic handling. The loose monoball allows for a large change in rear toe angle. I found out a week ago when out for a drive in windy weather. I found myself suddenly veering in the lane when a gust would push the weight side to side and effectively steer the car from behind.
How do you know it's the culprit: With the car on the ground, grab the rear wheel and push in and pull out. You don't have to push very hard either. Any motion and/or clicking in the rear suspension means you have a problem. Assuming the wheel bearings are OK, it is time.
You need to take the trailing arm off, remove the c-clip, and press the bearing out.
COM-10T, ~$5.00 each. Press the new one in, Reuse the c-clip. Add the weather seals, as they are no longer available. Reinstall the trailing arm.
When they are new, the handling is super crisp. Worth it. Lasted 45,000-50,000 miles with ~70 track days since 2004.