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Here is a comparison between the stock bushing on the left and the Whiteline part on the right.
The stock part is cut out and allows a lot of unrestricted motion. The Whiteline bushing is solid through the middle to positively locate the trailing arm but has cutouts to allow motion in the second degree of freedom to prevent binding.
Here is the Whiteline trailing arm bushing in place.
Next, the rear lateral arm and upper control arm links are removed.
The bushings are pressed out and Whiteline bushings pressed in.
Now, the lower control arm is removed.
The stock bushings are pressed out.