Checking the Rear Suspension For Wear
At least once a year you should check the rear suspension for wear. Remember these are old cars and things wear out. You have two places for wear to take place in the rear of the C4. The most common wear problem is the wheel bearings. Raise the entire rear of your car off the ground on jack stands. Now grasp the bottom and the top of the tire. Then try to wiggle the tire in and out. I've generally found that all C4s have a very slight amount of play in the bearings with the emphasis being on slight. After you repeat this process on the other side, you will now know if you need rear wheel bearings. With the wheel bearing diagnosis completed you should now place your hands on the front and rear of the tire, with one hand reaching all the way to the inner edge of the tire. Again try to wiggle the tire back and forth. You shouldn't have any play in the wheel.
If you find you have movement, you'll need to crawl under the car and locate where the play is taking place while your partner moves the tire back and forth. This wear can take place at the outer tie rod end or at the inner ball socket where the tie rod mounts to the differential cover. There are some specifications for the amount of play you should have in the rear of your Corvette but most of the time it's rather obvious. If you have serious wear you'll notice a huge difference from the right side to the left side. It's unusual for both sides to have serious problems at the same time. Then again these are old cars so use some common sense.
GM used two different types of toe control rods during the production of the C4. The early cars use a male tie rod end. In 1992 they switched to a different arrangement. The problem is that the parts for the early cars are no longer available. If your tie rod ends are worn on an '84-'87 Corvette, you're going to have to replace the entire assembly. You can also convert to a heim-jointed arrangement if you have a track only car.
The second area of concern with the rear suspension is the camber setting for the rear tires. The goal is to have the tires at a 90-degree angle as you go around a corner. If your tire is vertical to the pavement, then you have all of the tire's tread on the pavement.
The goal is also to have everything stay in place. You don't want things moving around as you drive through a corner. Camber changes in the middle of a corner are not fun. If your suspension is worn out, the bushings compress rather than transmit movement. This is a case where new bushings can be a big help. You can purchase a new set of bushings, or you can do as I did and purchase a whole new camber rod. I wanted the rapid adjustability, which you may not need. It behooves you to look at all of the options available to you.
Everyone sells polyurethane bushings. They're not very expensive, and if you believe the ads they're a miracle cure for your Corvette's handling. Let me just say that I've used them in every possible point on my suspension. Let me also say that if I had an alternative I would get rid of them. I would replace all of them with Delrin or even aluminum. Delrin is just much harder than polyurethane and compresses even less. The problem is that Delrin bushings are just not available, and I'm too lazy to machine my own Delrin bushings.