Originally Posted by ZoomZ

Polyurethane is not solid. It will move and it will eventually wear out. It's just harder than rubber. Under those pressures and stress, PU will flex.

Even solid metal bushing is suseptibel to wear. Specially where the center bolt meets the bushing. Over time the metal stud will eventually elogate the aluminum. Depends on how hard you launch and power going back there.

So I'd say keeping the diff from moving at all (or limiting it) will prolong any type of bushing.

Just rememeber, that force is being transmittted somewhere else. Looking at both the Z1 and Bell set up, all the force is transmitted to a singular bush/nut in a very thin subframe wall. Not ideal, but it simple.

GK tech has a better idea with a two bolt sytem. More work but better design. What im saying is, not to use a different cover, but using the concept of a larger bushing/through bolt for the Z1/Bell Diff brace attach to the subframe.

https://youtu.be/xJoZnto4J-8?si=JG7cv2ORSoXWzBVh

Skip to 6:25 for install.