Well finally got around to lowering the 84', decided I would shoot some pics and do a write up. Here ya go...
Materials needed, lowering bolts wedges and durable strips of rubber.
How to lower you’re C4 Corvette:
Lowering of the front:
First off, you need to get your Corvette's front end off of the ground. Try to get it pretty high off the ground because you will need to get under your car to take some brackets off. Place the front end on two jack stands and make sure that it is secure before removing the jack. Then remove your front tires, and if you have ABS you should remove the sensor as well.
Remove the one bolt that connects the sway bar to the spring retainer plate. Next, take the cotter pin and castle nut off of the tie rod end using a 21mm socket. Do this on both sides.
Take your jack and place it under the lower control arm and raise it until your shock compresses a bit. Be sure to put a piece of wood between the jack and lower control arm. Now you can use your 13mm socket to remove the two bolts attaching the shock to the plate. Then remove the cotter pin and castle nut from the lower ball joint using a 21mm socket. You will probably have to use a ball joint puller to disconnect the knuckle from the ball joint as well as the knuckle from the tie rod end. An automotive fork and hammer will also work, which is what I used. Slowly lower the jack and get it out of your way. Then you can swing the knuckle assembly out of the way and support it with a 2X4 if you wish. Now run to the other side of your car and do it again.
Now you can remove the metal retainer that the shock attaches to. There are 4 bolts that need to be removed using a 13mm socket.
Next, remove the two 15mm spring bracket nuts. The bolt will probably spin and an impact tool may be handy here. What I did was I took a 15mm socket and attached it to a universal, then attached that to a long extension. From the top on the driver side you wiggle it onto the bolt coming down through the engine compartment and wedge it onto the bolt. Then you can go back under the car and use another socket driver to loosen the nut. On the passenger side there is about a one inch diameter hole in the frame rail that you can squeeze your extension with universal down into and do the same as on the driver side. The other bolt you can reach with a wrench to keep from spinning. Remove these brackets and set them aside.
To free the spring from the lower control arm I just stepped down on the control arm and this pretty much separates the spring from it. Now you have to remove the spring by twisting it and sliding it back and forth to free it from the car. Be careful not to scratch the spring because doing so can jeopardize the integrity of it.
Now remove the two spring pivots from the spring and cut the rubber down to the thin metal shim.
Now you can glue the wedges in place of the spring pivots with glue that is both moisture resistant and somewhat flexible. I used weather sealant polyurethane. Having these wedges are critical to the performance of your Corvette. Since the original ones are designed to pivot the spring back and forth when the car turns, you will still need this pivot point, which is why the wedges are wedges and not a flat piece of rubber. They allow the spring to still pivot between the suspension and the frame itself. Now if there were no wedges and the spring sat directly against the frame then the spring rate will be disrupted, altering the springs designed purpose. Also, the direct contact to the frame will eventually damage the spring and put gauges in it, which will allow moisture to enter and deteriorate the spring. If you insist on putting the spring back in without the wedges, perhaps just leave a little bit of rubber as an impact point.
But there is a solution if you want to keep your spring intact and lower it more than the wedges will allow. I used a belt sander to sand down the bottom of the wedges and left about 3/16" plus the actual wedge as shown in the pictures. I then glued these down to the spring and allowed it to dry overnight.
Before sanding on the left, after sanding on the right
Homemade wedge sanding equipment
Wedges glued to the spring
84-87 Corvettes use a stamped steel spring bracket which is hard to modify when using these wedges. 88's and up use an aluminum bracket which is easy to shorten using a hacksaw. So, in order to fill the gap between the spring and the frame once the bracket is installed, I put a small strip of rubber on the inside bottom of the spring bracket to make up the difference in height that we lost from removing the spring pivots. Now when you screw these brackets in place there will be no gap and it should install tightly against the frame, compressing the rubber that we just installed into the bracket.
Assembly is the same as disassembly.
Lowering of the rear:
You don't even need to get the car off the ground to do the rear. First, take your jack with a piece of wood on top of it and raise the rear spring in order to take the tension off of it. note: driving the rear of the car onto ramps can help.
Now remove the cotter pin and castle nut (blue arrow) and slide the bolt out.
This is what will come out with the bolt. Make sure you remember how to put it back together.
Note where the old nut was located on the bolt, and mark it on the new bolt. Then, just experiment with how low you want to go by loosening and tightening the new nut.
You can still get a pretty low ride by trimming the wedges while maintaining the original pivot point and design of the spring. I was about 3.5" high in the front and rear before I started, now in the front I have a little less that 1.5" and the rear about 2".