1979 Chevy Corvette - Part 4: Kept In Suspense

With the parts prepped, rear-suspension assembly can begin

Chris Petris Jan 28, 2005 0 Comment(s)

Now the fun begins. All of the subassemblies are complete and ready toinstall onto the frame. The frame was cleaned thoroughly with xylenesolvent to remove grease and oil. Using xylene for cleaning can bedangerous; use it only in a well-ventilated area with no open flamepresent. We used a 3-inch orbital-style sander to remove minor surfacerust. Fortunately, there was no rust pitting on the frame.

Once the frame was clean, we applied Ospho rust preventative, which isgood for stopping rust and prepping paint. It can be applied with abrush or cloth, but don't leave any liquid. Rings or drips from rustpreservatives are almost impossible to remove. After applying thepreservative to the entire area, use a cloth to wipe off the excess.

Once the frame was prepped, we applied a coat of PPG DP90LF epoxysemigloss black primer to the frame. Add thinner to the epoxy primer forbetter flow and control of the semigloss sheen. The epoxy primerprovides durable protection without a topcoat.

The trailing arms, differential housing and cover, and rear spindlebearing housing pieces were powdercoated gloss black. All pieces wereblasted and powdercoated for $150, saving a lot of hard labor. Duringthis process, the correct-color topcoats were applied as necessary. Thepowdercoat base is durable and should prevent corrosion for many years.

The fun begins because the newly bought and cleaned suspension piecesmake assembly enjoyable. Before installing the differential, we put in adifferential drain plug for easy servicing. After the differential is inplace, the trailing arms can be installed. All of the bolts, washers,and nuts are being replaced. Split lock washers should always bereplaced because they lose their spring effect, diminishing grippingstrength.

When all the hardware is replaced, save the original bolts and nuts foryour NCRS buddies. All threads should be cleaned for proper tighteningduring assembly. An application of light oil during assembly preventsthread corrosion and allows proper torque.

We haven't selected a brake caliper, so we'll do the front suspensionbefore wrapping up the brakes. The brake rotors are aftermarket pieceswith a cadmium finish, so corrosion shouldn't be a problem for a while.We prefer to apply a high heat coating to the rotors for additionalcorrosion protection.

If aesthetics are important, wheel selection plays a role in the finishthat's applied to the calipers and rotors. We'll make a decision on thewheels before applying any color coatings to the brake pieces.

Parts are on the way for the front suspension except for the upper andlower control arms. We're considering Vette Brakes tubular A-arms. InPart 5 we'll discuss the front suspension overhaul.

Torque Specifications

Diff front mounting bracket bolts: 50 lb-ft

Diff crossmember to diff cover bolts: 60 lb-ft

Diff crossmember to frame bolts: 65 lb-ft

Axleshaft U-joint caps to diff bolts (inner): 35 lb-ft

Axleshaft flange to spindle flange bolts (outer): 65 lb-ft

Strut-rod bracket to diff mounting bolts: 45 lb-ft

Strut-rod shaft/shock mount stud: 75 lb-ft

Trailing-arm pivot bolts: 50 lb-ft

Wheel lug nuts, steel wheels: 80 lb-ft

Wheel lug nuts, aluminum wheels: 90 lb-ft

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A 5/8-inch hole saw is used to remove a piece of the strut-roddifferential mounting bracket. The pilot drill for the hole saw goesthrough the bracket and differential case. The pilot hole in thedifferential case is increased to 5/16 inch, so a 1/8-inch pipe tap canbe used for threading the diff case. Then a 1/8-inch socket-head pipeplug is used to plug the hole.

Bolt the differential crossmember to the diff and torque the bolts. Thenapply chassis grease to the differential mount cushions where they mountto the frame. The grease helps removal if necessary later. Once thecrossmember is in place, torque the bolts.

Install the trailing-arm bolts with long-tip needle-nose pliers. It'seasier to install the shims after the trailing-arm bolts are in. Ifyou're using rubber bushings, don't tighten the trailing-arm bolts untilthe vehicle is at ride height. Urethane bushings rotate like a bearingand can be tightened as soon as they're installed. Rubber bushings havelimited movement and should be tightened in their center of travel forlong life.

The emergency-brake cables must be installed after the trailing arms.The e-brake cable ends can't be installed once the rotors are in place.Once the e-brake cable is in, pull on each side of the cable to makesure the cable end seats into the e-brake lever at the backing plate.Pull on the cable once again after the rotors are installed to centerthe e-brake shoes.

Before putting in the axleshaft, the brake rotor should be installed andtorqued in place with all five lug nuts to allow rotor-runout checking.This helps prevent considerable aggravation when the axleshafts areinstalled, since it's difficult to turn the rotor during rotor-runoutchecking. Excessive rotor runout causes brake-fluid aeration and a low,spongy brake pedal. New rotors may need correction due to variations ofthe spindle-rotor mounting surface. Your hardware store should have .005brass shim stock that can be used for rotor-runout correction. Locatethe high spot and place a piece of .005 shim stock on the opposite-sidelow spot between the rotor and spindle.

Axleshaft installation is simple. Make sure the universal joint cups arein place on the diff side. The outside axleshaft yoke uses French locksfor bolt retention on '63-'79 cars, but 7/16-inch split lock washerswork equally well unless you're looking for NCRS or Bloomington Goldcertification.

The VBP strut-rod mounting bracket positions the strut rods lower toimprove camber control. When installing the strut-rod bracket to thebottom of the diff, be aware of bolt length. If the bolts are longerthan 3/4 inch, they can pierce the diff case. Use lock washers and flatwashers with the bolts for correct bolt stack height.

A rough alignment can be done with simple tools before a trip to thealignment shop. Use a 24-inch carpenter's bubble level to check camberby placing the level flat against the tire. If the bubble is close tocenter, the car will handle safely. Improper camber can make a car feelscary. Use a tape measure to check toe-in. Measure from the center ofthe tires at the front, then do the same at the rear. A quarter-inchdifference in the measurements front to rear is safe and won't wear thetires excessively. Incorrect toe settings can cause tire wear as well,so checking the camber and adjusted toe is a must.

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