Whenever they have failed.
The trailing arms are what holds the rear end/axel on. The bushings are what allow movement of the arms.
it is part of the trailing arm, not sold separately. part #15292403 right side, part # 15292404 left side.
It is most definately dangerous.
It means the rear trailing arm bushings are worn out and if that is the case the rear end won't track properly. The vehicle will appear to "dog" track.
The rear suspension Trailing Arm bushings are likely worn out and/or the rear shocks are in need of replacement. There is an upper and a lower trailing arm on both sides of the vehicle in the rear suspension. As a test, grab a firm hold on the lower trailing arm and try to twist it. If your able to move it even a little, the bushings are shot.
When your rear trailing arm (rear control arm) are bad you will hear a clunking noise when going over bumps and potholes .... This noise is louder and more noticible while you have passengers in the rear seats..... You will also hear your tires squeek a little on turns
bad trailing arms or bushings,or bad struts!!
You may replace the bushings by pressing them out or replace the knuckle assembly. Pressing out the old bushings and replacing them is the least expensive option. After market replacement
For any type of bushings you will need a special tool to take them off the bushings are pressed in
You may replace the bushings by pressing them out. GM would rather you not know this!!
When the rubber bushings have deteriated and are no longer doing their job.
Replace the bushings in the track bars that connect the rear axle to the vehicle.