Hi Folks,
May I suggest you try a search on this and related topics? There are probably hundreds of posts relating to bushings, and I think you'll find these to be very useful.
I've experimented with GM's stock high-loss OEM bushings, polyurethane, and delrin at virtually every bushing location on the car. (I never tried aluminum, due to the spontaneous electrolysis it creates where it contacts steel.)
In general, the factory's high-loss bushings work best to isolate the frame from the body to create a smooth ride. Polyurethane is not very lossy, and therefore efficiently transmits frame/suspension resonances to the cabin. In a word, it can create a very jiggly (although admittedly "stiff") ride. It's not comfortable on the street, I think - especially if you have low-profile tires and polyurethane bushings in the suspension to begin with, as I would think is quite likely for many readers here. On the other hand, with stock tires and stock suspension, the polyurethane body bushings may work well, although I wouldn't know as I've never tried this particular combination.
The factory bushings excel at isolating frame/suspension deflections and resonances from reaching the cabin. But the flip-side of this characteristic is that the frame (which is very floppy to begin with as it was designed by GM,) therefore derives little stiffness from the body. This results in a pronounced sensation of vagueness of handling and looseness, particularly in the front end (added triangulated braces notwithstanding.)
After many years of experimentation, I've found the following offer the best combination of ride comfort and effective frame/body coupling for crisp, predictable handling, with low-profile tires, and stiff suspension bushings:
1.) Radiator support: hard coupling using delrin bushings.
2.) Firewall bushings back to penultimate rear bushings: stock,
(but stiffest) rubber bushings, top/bottom all, plus "missing"
axle bump bushing.
3.) Rear-most bushings: polyurethane.
The biggest departure from traditional approaches is the extremely stiff front bushing. The difference this one trick makes is profound. Front-end vertical bending stiffness nearly * triples * as a result, and steering will be much more precise than one would believe possible with these cars! If one most compromise here, then the next step down is to use polyurethane, but the degradation is noticeable, manifested in a partial return of front-end "jiggliness."
Hope this is helpful.
Best,
MAP
It wasn't too bad, but I squirted penetrant up at the nuts for a couple days while they were shipping. Removed bumpers, made a tool like on gnttype, don't raise left side up very high (just enough to get the old one out and new one in) to save the power steering pump. Glad, VERY GLAD I did them all, because the uppers vere in horrible shape.(didn't look too bad until I got them out
