Refurbishing the Rearend on a 1985 Corvette

Our Project ’85 Gets New Bushings and a Complete Rearend Cleanup

Andy Bolig Dec 1, 2000 0 Comment(s)

Step By Step

Once you remove the wheels, you can basically remove the entire spindle assembly and driveshaft as a unit. We removed the bolts and caps that hold the driveshaft to the differential yokes, the bolts to the sway bar, and the emergency cables first. Loosening the spring bolt and the outer tie rod was next. Typically, the shocks will keep pressure on the spring. Jack up the rear spindle housing and remove the lower shock bolt, or remove the spring bolt. Either will relieve the pressure on the spring. Once they’re removed, there are only three bolts holding the assembly on. Remove the lower strut rod and the two trailing-arm bolts, and the assembly and driveshaft will come out.

It’s much easier to remove all of the strut rods and trailing arms with the assembly sitting on a workbench. Here, we’ve removed the strut rod and the trailing arms.

Now remove the spindle from the bearing. Do that by removing the cotter pin and keeper. To remove the nut that holds the spindle in place you may want to use an impact gun. They’re torqued to 81 lb-ft. Once the nut is removed, simply tap the end of the spindle and it will slide out.

When we removed the U-joint caps, we were glad we’d decided to change them. They had been run dry for quite some time, and it showed. Rust does not lubricate very well.

Another problem was that the bolts that held the U-joint in place were tight and the heads were stripped, so we had to cut the heads off and use vise grips to turn them out.

We separated the bearing from the outer housing by using a Torx bit on a pneumatic gun. Once the three bolts are removed, the housing will fall into three pieces.

The bearing, the emergency brake, and the housing will fall apart from each other. At this point, the best thing to do is clean, and the best thing we found for cleaning up the parts is a Scotch-Brite pad in a parts washer.

As with the front, the original bushings were replaced with polyurethane ones supplied by Vette Brakes & Products. The trailing-arm bushings were removed by cutting two flat spots on the side of the bushing that would be on the bottom while positioned in the press. This gave the trailing arm a flat surface to rest on while we pushed out the bushing from the other side.

The lower strut rod’s bushings popped right out with a screwdriver once the metal sleeve was pushed out.

We pushed the new bushings back in, but you have to be careful to put the right size bushings in because the inside diameter of the sleeve is different.

We pulled the differential housing to replace the seals. Because there was no transmission in the car, after we removed the four bolts for the spring and the three bolts that held on the tie rods, the only bolts holding the differential in place were the two at the end of the differential carrier. A jack will definitely be your best friend once you pull out the bolts.

With the differential on a workbench, we removed the carrier from the differential to inspect the gears and to allow removal of the yoke shafts.

When you split the case, all of the differential fluid will come pouring out, so place the differential over something to catch the fluid.

A set of snap-ring pliers is necessary to remove the retaining clips that hold the yoke shafts in place. The snap rings come in seven sizes for the model 36, and eight sizes for the model 44 rears. Each size snap ring is a different color and they act as shims to control the yoke-shaft endplay. The best thing to do is tag each clip and yoke so you know which side it came from.

With the yoke shafts removed, the seals can be pried out with a seal hook. We had to tap and pry on the one side to break the seal loose. Be careful not to damage the differential housing. When putting in the new seal, we coated the inside of the seal groove with Permatex Aviation Sealer to prevent leaks.

Installing the seal can be tricky because it has a dust cover built into the seal that prevents tapping on the seal’s outer surface. Chris Petris of Corvette Clinic has located several sizes of brake-caliper pistons that work well to tap in seals. These are ingenious tools that will cost next to nothing at the salvage yard. With the seals installed, you can reinstall the side yoke shafts and clips. Make sure the clips are seated fully in the groove before you continue.

We also removed the driveshaft yoke and replaced the seal in the front of the differential. Removing the nut can be a bit of a challenge because it’s torqued to 190-210 lb-ft, and it’s important to keep the front yoke from spinning. Tasks like this can make friends or a mechanically inclined wife invaluable. Once the nut and seal are removed, the new seal can be coated with Aviation Sealer and installed. This seal can be tapped in with a gently wielded hammer, but be careful to tap in the seal evenly so as not to distort the seal. Have your friend/wife help you tighten the nut on the front yoke to 190-210 lb-ft again. Once the nut is tight, the rotating torque of the differential yoke should be 15-35 lb-in for model 36 and 20-40 lb-in for model 44 rears.

To replace the bushings in the differential carrier, press out the rubber bushings and then remove the metal sleeve left inside the opening.

This is done by curling over the edge of the sleeve in several spots and using a large socket with the aid of a press to push out the sleeve.

Then simply install the urethane bushings.

Now you can install the differential to the carrier. Use Permatex gasket material to seal the two halves together. Torque the bolts to 21-24 lb-ft for model 36 and 32-38 lb-ft for model 44 rears.

We replaced the seals in the spindle-hub assembly. They were simply tapped out from the back and the new ones tapped evenly back in place.

The outer tie-rod ends were replaced by breaking the jam nut loose and turning out the tie rod. Before you install the new tie-rod ends, run the nut on the new tie rod to the same place as the old one. This will require only minor adjustment when you get the car realigned.

We used Brute Force U-joints on Chris’ recommendation. He has had excellent results using them in his shop.

We assembled the hub assemblies with the new wheel bearings supplied by Corvette Central. The three Torx-head bolts hold everything together. Torque them to 59-73 lb-ft.

When you install the spindle into the hub, do not put any pressure on the bearing until you torque the spindle nut to 81 lb-ft, meaning that you don’t want to put the wheels on the rotor to tighten it. Once you have the knuckle housing assembled, you can install it on the car. Tighten the trailing arm bolts to 55-70 lb-ft to the body and 125-154 lb-ft to the bearing housing.

Install the differential carrier and torque the bolts to 81-118 lb-ft. Again, a jack can be a big help.

While you have the jack handy, jack up the bearing assembly and install the halfshafts. Once all the bolts are tight, install the lower strut rod to support the housing once you lower the jack.

Fasten the tie-rod housing to the differential carrier with the three bolts. They should be torqued to 50 lb-ft.

Install the spring, making sure to have the same number of shims on each side. Torque the bolts to 32 lb-ft.

Install the spring link bolt next. Screw the nut on just until you can get a cotter pin installed in the hole through the bolt. This photo shows the nut on the top, but GM typically installed the nut on the bottom at the spring. You can also install the tie rod into the knuckle housing and hook up the sway bar at this point. The tie rod should be torqued to 32 lb-ft. Be sure to put a cotter pin in to keep it from backing out. Also, we installed new shocks from Corvette Central to improve the ride. If you’re putting new shocks on your ride, this would be the time to do it.

Don’t forget to fill the differential with fluid. The limited-slip differential requires 4 ounces of GM additive PN 1052358 installed first, and then topped off with SAE 80W lubricant.

When the fluid reaches the fill hole, the differential is filled.

You’ll notice that this photo shows the wheels installed, but we have not reinstalled the brakes. We’re currently working on a brake system that will upgrade the rear brakes while utilizing factory GM parts. Look for that one in an upcoming story.

When we first took on this project, we knew we’d be putting some miles on the car. We wanted to make sure it was reliable enough to drive pretty much anywhere. Going through the rear assembly and replacing all worn parts was the only way to achieve that level of reliability. The rear was in pretty good shape but since we had it all disassembled for inspection, we contacted Corvette Central to replace the worn parts. We installed polyurethane bushings and took the time to clean everything to bring the car’s rearend to like-new condition.

Check out the photos and captions to follow our progress.

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