Polyurethane and Leaf Spring Main Eye Questions 1976 C25

[Gdubs997]

Hey so I am considering buying polyurethane bushings for my trucks suspension, have many of you done this? I've looked a few places on the forum and don't know what people's thoughts are about them.  I feel like they should be fine but am not sure what they will do for the truck that rubber wont do other than not corrode as fast.  Also, apparently there are two different main eye sizes for the leaf springs, does anyone know how I can figure out what mine is? Is the main eye the whole the bolt goes through when connecting the leaf spring to the shackles?  I can't find information anywhere on sizing and it's hard to determine the size of mine while it's still on the truck (I'm working on taking the rear differential off right now but am not done yet).

[bake74]

     Welcome to the site.  There is a difference between regular rubber and polyurethane.  You are right they do last a lot longer.  Also when they get older, they do not squeak and make noise as regular rubber bushings will.
     I also found out something about the polyurethane bushings in regards to color vrs black.  Black is the natural color when they make the bushings.  Dye is added to the bushings to make the different colors, the dye actually dries out the bushings some, which leads to the possibilities of drying out faster and making noise down the road from being dry.  (ie, the squeaking like regular rubber bushings will).

[pholliday1]

Poly is a big upgrade, for a couple reasons. Rubber is doomed from the start and will eventually degrade. If the rubber is degraded then the suspension cant properly move. A lot of the ride quality comes from the first couple of inches of suspension movement. In A perfect world your springs & spring shackles will have poly bushings and the bolts and bushings will be lubed. Also the bolts that hold everything together would have lock nuts so that the suspension is bolted together but not "squeezed" to the point that the spring eyes cant pivot. Lastly in this perfect world your leaf springs would be lubricated in between the leafs so they can "slip" back in forth with out hindrance from the mounds of rust that gets between them. 

[Gdubs997]

Thanks guys I'm very excited to be part of the site and even more excited to get my truck restored!  I'm all for black polyurethane bushings then for the suspension, I'm going to leave the body mounts as rubber because I've got polyurethane engine mounts in my volvo and it ended up transferring a lot of the vibrations into the cabin and I want to avoid that on the truck. 

Does anyone know about the bushing sizes in regards to the main eyes? Is there an easy way to find out what size mine are?

[Mario]

I've had polyurethane bushings on the front springs for a few years now, and recently added them to the rear.  They say it's a rougher ride, but I haven't noticed.  It's a dang 3/4 ton truck, not a Cadillac, haha.  Energy Suspension has a PDF catalog that will show the various options on leaf spring eyes based on weight capacity.  Here's the deal:  Main eyes can be 1.5" or 1.75", rear eyes can be 1.5" or 1.375", and the same for the shackle eye.  Anyway, go measure the best you can, just call them and verify what part number you should be ordering.  Ohhh, and plan on burning the old rubber bushings and sledge hammer work out.  Good luck, Man!