The fastest wearing rear suspension part on 1963-’82 Corvettes is the strut rod bushing. The rubber A-arm bushings in the front suspension last longer because they only deal with rotation about their axis. In comparison, the small rubber bushing in the strut rod deals with both rotation and twisting as the suspension moves up and down. Wear in these inexpensive bushings is not much of a safety issue but it does change the rear wheel alignment, which could cause excessive wear on those very expensive tires.
The strut rods and the halfshafts are the two rear suspension members that determine how the tires contact the road. As the bushings wear, the bottom of the tire extends farther out with respect to the top of the tire. This negative camber causes premature wear on the tires’ inner tread.
Although this article focuses on how to replace strut rods on C2s and C3s, the procedure is similar for most other generation Corvettes. The parts options are also similar and include rubber or polyurethane bushings and adjustable strut rods. Zip Products joined with us on this article as they offer a full range of stock and performance parts for all generations of Corvettes.
Strut rod replacement is relatively easy to do. No expensive special tools are needed. This repair requires only the removal of three nuts per side (or one more nut if the spring is disconnected). And it can be done without a lift. Just be sure that the car is securely supported by jack stands when it’s raised because a degree of pushing, prying and hammering may be required, particularly on the shock mount. Follow along as we get down and slightly dirty repairing one of the prime trouble spots in Corvette’s independent rear suspension. Vette
Zip Products offers two types of replacement bushings for 1963-’82 Corvette strut rods: rubber and polyurethane. Note that the replacement rubber bushings (bottom left) have a steel sleeve around them to enable installation in original rods and therefore the rubber is thinner than found in the original bushings.
Zip also offers new strut rods with bushings already installed. Adjustable struts rods with polyurethane bushings are shown here along with reproduction strut rods that have rubber bushings. Note that the adjustable struts rods can be set to a shorter length, which may be necessary to correct the rear-wheel alignment due to wear in other rear suspension components.
The spare tire assembly was removed to make photographing easier. While not necessary for strut rod replacement, it comes out after the removal of only two bolts. Removal allows you to clean out the dirt and debris that has accumulated over the years and to check the condition of the spare tire.
Remove the cotter pins from the spring bolt and shock mount on each side. Tip: wire cutters work best at bending and prying out rusted cotter pins. Four new 1/8-inch cotter pins, 1-inch or longer are needed during reassembly.
Although not essential, it’s easier if you disconnect the spring ends. An 11/16-inch open end wrench holds the top of the spring bolt. If a sway bar bracket is attached, a thin wrench will be needed to get in on the bolt head.
Loosen the spring bolt nut while the jack is out of the way but leave it attached by at least several threads. Note that the large thick washer has the rounded edge next to the cushion. While this orientation is not critical, that’s the way it came from the factory. Also note the polyurethane cushion. The stock rubber cushion compresses and deteriorates over time but this cushion is still like new even after over 10 years of service.
Use a 15/16-inch socket with a breaker bar to loosen the castellated nut on the shock mount. Then use a 3/4-inch socket to remove the nut at the bottom of the shock absorber. Tip: it’s easier to remove these before disconnecting the spring.
Tip: place a clamp on the inboard side of the spring to prevent the jack from slipping off as the spring is lowered. Some springs, especially those with lower spring rates, are steeply arched and when they are released they can kick the jack out.
Remove the nut, lock washer and beveled washer from the shock mount. Removal of the beveled washer may require turning or prying because it often gets jammed. Make sure to remove both washers to ease removal of the shock absorber from the mount.
Jack the tire or trailing arm up slightly to take the weight off the shock. Pry the shock off the mount, contacting only its lower end to prevent denting the cylinder. Be aware that air shocks may extend a little farther down when disconnected.
Try using a pickle fork to tap the shock mount out from the bearing support. Removing the shock mount is the step in strut rod replacement that can give you the hardest time if it’s rust-seized to the bushing’s inner sleeve.
Alternately, reinstall the castellated nut backward and flush with the end of the threads and then tap cautiously on the nut to break the shock mount free. The reason for reversing the nut is because of the castellated holes; that end is easily mushroomed. Before designing a removal tool for this, I used to weld a plate on the end of a nut to do the job without damaging the shock mount.
Option three to remove the shock mount involves the use of an air hammer, if you have access to one. Zip offers a tool to help break loose rust-seized shock mounts without harming the part. Screw the tool onto the end of the shock mount, lock the shaft into the air hammer and knock the shock mount out. After removing the shock mount, pry the outer end of the strut rod from the bearing support.
Remove the nut and washers from the inner end of the strut rod and then tap the camber adjusting bolt out. Two reducing washers should fall out when the strut rod is removed. All too often they are lost or forgotten during reassembly.
The reducing washers are necessary because the diameter of the camber adjusting bolt is smaller than the shock mount bolt and both go through bushings of the same size. Zip offers new reducing washer replacements and a camber adjusting kit. Note that the 1975-’82 washers have a larger OD to match the larger, later bushings.
This rubber bushing is completely worn out between its inner sleeve and the outer end of the strut rod. This is the normal mode of failure, and all four bushings looked like this. This wear increases the effective length of the rod, which is then often more than the camber adjusting bolt can compensate for.
It was necessary to grind a little off the inner sleeve and to trim the poly bushing to fit into the bearing support. This might not be necessary on 1975-and-up C3 bearing supports, which were designed for larger strut rod bushings.
Install the shock mount through the strut rod and reattach the shock absorber. Tip: raise the wheel or trailing arm to make installation of the inner end of the strut rod easier. Note that rubber bushing strut rods should be raised to normal ride height before the shock mount nut and camber adjustment nut are tightened.
The adjustable strut rods from Zip come with a parts kit that replaces the stock camber adjustment parts and includes the reducing washers. One side of each plate had to be ground slightly to fit into this strut rod bracket. Better snug than loose here.
Tip: after installing the inner end of the strut rod, check the tightness of the strut rod bracket bolts while you are there. These bolts loosen so frequently that I make sure to check them with every C2 and C3 suspension inspection. I strongly recommend applying a threadlocker to these four bolts in addition to using their stock lock washers.
Recheck the tightness of the four nuts on each side and install cotter pins in the spring bolt and shock mount. Replacement of the strut rod is now complete and the new polyurethane bushings are certain to last a long time.
Turn the center sleeve on the adjustable strut rods to set the camber angle. To make adjustment easy to remember, the rods were installed so that pulling the 7/8-inch wrench back pushes the bottom of the wheel out.
Camber is easily measured using a level held against the wheel. Factory specs call for a small degree of negative camber; that’s when the wheel is tilted in on top. Adding even more negative camber improves cornering. (You’ll see wheels titled in considerably on cars set up for racing.) However, we set it to zero for optimum tire life, and because the camber will go negative as the new bushings wear in. This wear happens quicker with rubber bushings.
A half turn of the sleeve on Zip’s adjustable strut rod changes the camber about 1/2 degree, which is nearly 1/8-inch measured at the wheel. Tip: mark each side of the sleeve to help count the turns. Use a large, adjustable or 1 1/8-inch wrench to tighten the lock nuts after adjustment.
A complete polyurethane suspension bushing kit is available from Energy Suspension for 1963-’82 Corvettes and later models. The bushings are offered in red or black.
Photography by John Pfanstiehl