Hello. I've tryed to install a couple of Super Pro differential poly bushing on my Miata, but i found that they had a fairy amount of play when the diff was reinstalled.
Turned out that the inner bore went bottomed before the bushing body, so the latter didn't got compressed.
I have stripped the bottom closing plate of the bushing from the triangle-shape rubber like i've watched in every video of bushing fitting. But this Super pro bushing have a strange shape on the bottom part, so that the plate touch only the inner part.
I suspect that on those bushings i had to keep the rubber. Any experience or thought from you guys?

 

Im looking at the same bushings on my bench and what to know what you find before I begin installing mine. My plate was so rusted that I'm looking for replacements before I attempt. I searched and found this thread needing to know exactly this answer........

 

Jeeze, I hope you had a close look at the subframe in the light of those! The car see (seen?) ice/salty roads?

 

As sad as it is, I would call this "normal" for middle Europe/UK cars with salty roads in the winter.
Mine weren't much better, but my car "only" had ~120k miles.

 

I guess that those bushing must be mounted keeping the rubber on the plate. It's the only way they can work.
Personally i've buyed an another couple of bushing, delrin style, and they fitted just fine without the rubber.