Here is the original frame...
Here is the original frame rearend being disassembled and removed from the chassis. The attaching bolts were badly rusted so we soaked them with a penetrant for a day before trying to break them free. The rubber bushings were rotted, allowing the rear springs to move around under acceleration.
After the frame was painted,...
After the frame was painted, we started the rearend installation by hanging the new de-arched Eaton spring from the front hanger on each side. New bolts were cad-plated and installed through the new rubber bushings supplied with the springs.
With both leaf springs installed...
With both leaf springs installed at the front mounts, the rearend was moved into position over them. New rubber bushings from Eaton were installed in the shackle mounts to the rear of the frame.
The detailed Plymouth Road...
The detailed Plymouth Road Runner rearend was wheeled into position on the floor jack. A rubber pad was used under the pumpkin to prevent damage to the fresh paint. The new Eaton U-bolts were cad-plated with the other attaching hardware. New rubber bushings had been installed in the rear leaf spring eyes. The rearend must be jacked up high enough to allow the springs to be secured to the rear hangers and mounts.
The original cad-plated hangers...
The original cad-plated hangers were then installed in the rear spring mount (one stud through the mount bushing and one through the spring eye bushing).
A bit of white grease will...
A bit of white grease will help the studs slide into place, and provide lubrication during use.
A rubber hammer should be...
A rubber hammer should be used to seat the hanger into the rubber bushings. Then the nuts can be installed.
At this point, the inside...
At this point, the inside rear hanger, front and rear mounting bolts, and nuts were secured. The rearend was still sitting on the floor jack above the leaf springs.
The rear axle housing pad...
The rear axle housing pad on each side was then positioned on the pin supplied on the leaf spring. The rearend was then slowly lowered onto the spring and the pin and the U-bolts positioned for the lower shock mounting plates.
The U-bolts were passed though...
The U-bolts were passed though the lower mounting plates and the nuts were installed. These U-bolts and the shocks keep the rearend positioned in the vehicle. Notice that the shock mounting studs are facing the front of the car.
Once the U-bolts and lower...
Once the U-bolts and lower plates were correctly positioned, the nuts could be progressively tightened. The best method is to work your way around the four nuts, tightening each the same amount on the threads until they are as tight as possible. Air tools are not required but make the job quicker.
With all the components secured...
With all the components secured tightly, the rear wheels were installed. We threw on a set of polished American five-spoke mags, shod in BFGoodrich tiresvery cool for the contemporary cruiser.
Here is the completed assembly...
Here is the completed assembly waiting for the KYB Gas-A-Just shocks to be installed.
The body must be in place...
The body must be in place because the top mount for the rear shocks is on the body floorpan. The original springs had four leaves each. The new Eaton springs have five for added support.
After 40 years, most classic Chevy rearends have been kicked, smashed, exploded, morphed, or otherwise mutilated. Occasionally they are treated to a wash and repainting, or stuffed with new gears for better performance. In general, however, they are the neglected end of the vehicle, and many times the first thing to break during an "exhibition of speed."
The technology involved in hanging a 40-year-old rearend and installing the suspension parts is relatively simple, but it must be done correctly. Old springs and cracked or damaged brackets, shackles, or U-bolts must be replaced, and an upgrade to KYB Gas-A-Just gas shocks will certainly add to the overall ride and handling.
Not much keeps the heavy rearend attached to the vehicle, so the parts must be strong and able to take the pounding supplied by a stout engine. Axle wrap-up (or hop) during hard acceleration can be a problem, so new rear leaf springs and good shocks are definitely required equipment.
Since our '57 is going to be lowered 4 inches all around, a set of custom springs with the de-arch built in was ordered from Eaton Detroit Spring. The built-in de-arch maintains the spring strength and integrity in the suspension without using lowering blocks or strange hangers at the front and rear spring mounts.
The complete original chassis was thoroughly sandblasted prior to being disassembled (clean metal is so nice to work with). The chassis will receive several coats of POR-15 glossy black before we start the frontend and rearend rebuilding. Most of the attaching hardware was sent out for cad-plating prior to the rearend installation to add that Rod & Custom touch of flash.
This chassis had been equipped with the original '57 GM 10-bolt rearend but due to its poor condition, we replaced it with a Chrysler rearend with Posi-traction and 3.23:1 gears. Luckily this Plymouth Road Runner rearend was the correct width, so it will be used in the '57.
As you will see, the installation is straightforward, but a prescribed sequence must be followed to avoid difficulties. A floor jack, jackstands, and normal handtools are necessary to do the job. This project might be something you would do to your classic Chevy--even if you're not building a '90s street machine.