In our last installment on “Scarlett,” our 1972 coupe project car, we started setting up the front suspension to make the car handle better, adding a heavier Addco sway bar and coil springs from Muskegon Brakes. We also installed Energy Suspension bushings to keep everything moving without excess deflection, along with 17-inch alloy wheels from Summit. The latter were shod with 275mm-wide BFGoodrich tires in place of the 215s the car came with. Having greatly improved the available grip up front, it was time to get to work on the rear.
Before we get into the how-to part, a word of caution: This is dirty, tedious, physically demanding work. It’s hard, it’s painful, and even after taking a toothbrush to my bruised hands when the project was done, it took days to scrub off all the grease. I’d always heard people complain about rear-suspension work, but having swapped out many of the components before—spring, sway bar, shocks, and more—I failed to enter this project with the appropriate degree of trepidation. Simply put, I hadn’t pulled the trailing arms before.
Tearing down the rear in Scarlett took almost six hours—three of them spent getting to the trailing arms, and another three spent getting them out. With the mix of disintegrating bushings, rusted-together alignment shims, and parts that appeared to have been assembled on the frame prior to the body drop, only one of the cross bolts could be removed; the driver-side arm had to be cut out of the car. So consider yourself warned: There’s a reason mechanics charge—and get—a lot of money for this job. And depending upon your financial position, mechanical inclination, and pain tolerance, it may very well be worth it to pay someone else. Personally, I’d still rather do it myself.
Now on to what we’re doing and why. The purpose of an independent rear suspension is to keep the tire perpendicular to the road, even while the car rolls toward the outside of a curve. This is done by causing the tire to gain negative camber—or lean inwards at the top—as the suspension compresses, which compensates for the car’s outward roll, keeping the tire relatively square to the roadway. In the shark suspension (as in the midyear before it), there are three links that control the angle of the wheel: the axle halfshaft, the camber rod beneath it, and the trailing arm.
The axle halfshaft floats in and out, which causes undesirable slack in the suspension. Unfortunately, that’s an inherent part of the design and can’t be changed without surgery well beyond what we’re doing here. The other two links, however, can be improved. The factory camber rods, which are usually adjusted by means of an eccentric locking system, have already been replaced on Scarlett with a pair of easily adjusted camber rods from Vette Brakes. The trailing arms, meanwhile, will be replaced with a coilover conversion from Van Steel, which accomplishes several different things.
Available from Muskegon Brakes, the Van Steel conversion comes with a new pair of trailing arms, as well the coilovers and adjustment tools. Coilovers are shocks with coil springs that encircle the shock tube and are mounted directly to it, usually with a spring perch that mounts on threads on the body of the shock. By connecting the two, the shock can more effectively dampen the action of the spring. And since it’s all a single unit, it’s easier to install and easier to adjust for ride height.
Another advantage on the C2/C3 platform is that the kit does away with the factory transverse leaf spring. The spring ties the two wheels together, which effectively reduces some of the independence between them, and with wider wheels such as the 17x9-inchers we’re using, the ends of the spring interfere with fitment. When we originally put the wheels on, we had to jack up the height of the rear spring—and ride height with it—by about an inch to make the ends of the spring clear the tire sidewall. And the tire-clearance thing isn’t just academic: Having once had a rear spring bolt rip the sidewall out of a tire on my old ’71 big-block, I’m especially grateful for the added clearance offered by the coilovers.
The Van Steel conversion is available for both small- and big-block applications, and with single- or double-adjustable shocks. While Scarlett is currently powered by a 350, we’re building an LS motor that will produce enough power to justify the stiffer big-block springs, so that’s what we selected, along with the single-adjustable shocks.
Once the trailing arms were removed, we shipped them off to Van Steel for the bearings to be rebuilt and installed in the new trailing arms. (If you plan to do the bearing swap yourself, you can follow the directions included with the kit for this portion of the job.)
With the completed conversion in hand, there were a number of obvious improvements in the basic setup (in addition to the obvious ones such as the fresh bushings). First of all, the folded-sheetmetal construction of the factory arms was replaced with ¼-inch-thick steel, with welded reinforcement ribs on the inboard side of the arm. Additionally, the arms were contoured to allow clearance for wider tires, and the parking-brake bracket was relocated to the top of the arm, moving it away from the sidewall.
The arms came fully assembled with the rotor run-out checked and the rotor marked for correct reassembly, as well as with new parking-brake hardware installed. Frankly, the whole setup looked so good I was reluctant to put it underneath a car, especially one that I drive in the rain. But things are meant to be used.
For details on the teardown process, see the accompanying photos. In the next installment, we’ll install the new rear suspension, and see what kind of difference it makes.
01 With the car securely on jackstands, remove the rear caliper, starting by detaching the brake line where it’s clipped into place on the trailing arm (visible here behind the parking-brake bracket). While there’s usually a hard steel line from the caliper to the soft line on the arm, our Wilwood calipers use a braided steel line instead.
02 Unscrew the hard line (or, in this case, the braided steel line) from its fitting, and pry out the clip that holds the soft line in place in the bracket. Be ready for the brake fluid that’s about pour out. Rather than crimping the line closed, I zip-tied a plastic bag around it. As much fluid as I lost, I’ll be ordering a case of Wilwood brake fluid to refill the system, so…crimp it.
03 Unbolt the caliper and lay it to one side, making sure to keep track of the bolts that hold it in place. Although you can do it later, now is a good time to remove the parking-brake cable from the trailing arm.
04 Remove the “Mickey Mouse” clip that keeps the parking-brake cable in its bracket—this one has already been pried over to one side—and pry the cable out of its armature on the hub. Depending on the condition of your parking brake, this may require some force to do. Remove the cable from its bracket, which you’ll notice has been relocated to the top of the trailing arm instead of its factory location on the side. This modification allows for greater wheel/tire clearance.
05 Since Scarlett had safety loops to protect the underside of the car in case of a blown halfshaft, I next removed them, starting by removing the two bolts that held them in place on top of the trailing arm.
06 The bottom of the halfshaft loop mounts to the other end of the shock mount, and is removed by simply backing off the nut. While the shock mount itself will have to be removed, this job will need to wait until the shock is off and the rear spring is out of the way.
07 To remove the shock, back off the nut that holds the bottom of the shock in place.
08 Pry the bottom of the shock off of its perch. While the Van Steel instructions suggest starting at the bottom (and that’s what I did), the Haynes manual suggests removing the top first, and this may be easier.
09 Now for the rear spring. While the factory multi-leaf steel spring has been replaced with a composite one, the same procedure applies for both, though you may wish to use more caution with the composite one. Note the extra nut, and how high the spring sits on the bolt—not optimal, but necessary for tire clearance in my case.
10 Before jacking up the bottom of the spring, which will reduce tension on the whole assembly, it’s wise to insert an open-ended wrench in the top of the trailing arm to keep the spring bolt from rotating while you unscrew the nuts from the bottom. It may be possible to clamp the bolt in place with a pair of vice-grips, but even that’s not a sure thing. The wrench is easier, but may require some prying and wiggling to get into place against the rubber bushing beneath the bolt head.
11 Use a jack to compress the spring. If you’ve got a composite spring, be careful to place the jack somewhere where it won’t damage it. Remove the cotter pin and castle nut.
12 With the nuts, bushing, and washer removed, slowly lower the jack, freeing the spring from the bolt. As with any other automotive spring, understand that it is under a tremendous amount of tension, and be very careful with it: If it slips off the jack while compressed, you could be seriously injured.
13 With the spring at full droop, slip the spring bolt up and out of the control arm.
14 With both sides of the rear spring disconnected from the trailing arms, remove the four bolts that hold the center of the spring to the frame. Be aware that there’s a bracket as well as spacers on both the top and bottom of the spring.
15 Remove the spring and gleefully cast it aside. Contemplate the puddle of brake fluid visible in the background, and be glad you crimped—rather than covering—that brake line we mentioned earlier.
16 To remove the shock mount, which also holds the strut rod in place, first remove the nut. (Recall that I did this earlier while unbolting the halfshaft loop.) Here, you can see the nut bracket hanging freely to the right of the mount.
17 To remove the shock mount, you’ll want the removal tool (around $20) and something along the lines of this short-handled sledge, which we lovingly call “The Motivator.” The tool screws over the threaded end of the shock mount like a nut, protecting the threads. You then whack it with the hammer until the mount comes free.
18 The shock-mount removal tool in place. While not absolutely necessary, it costs less than half of what a replacement shock mount does, making it a good buy.
19 The shock mount after removal. Remember how far behind the mount the spring sat? The advantage of a coilover is that it combines the spring and shock into a single unit, eliminating the tenuous connection between the two in factory form.
20 Disconnect the four bolts that hold the halfshaft to the hub. These will most likely be extremely tight, so anticipate using a breaker bar. While the directions say to disconnect both the inboard and outboard ends of the shaft, freeing it completely, I opted to only unbolt the outboard side.
21 Now for the trailing arm. This is the driver’s side: Note the painted-over pivot bolt, and the head of the large cotter pin that’s visible near the bottom of the photo. It holds the alignment shims in place.
22 After removing the nut from the pivot bolt, remove the cotter pin that holds the shims in place and pry them up so they can be removed. The square ends of the alignment shims are just visible beneath the trailing arm, having already been rotated part of the way upwards. Depending on the amount of rust present, you may not be able to free them until the trailing arm is out.
23 On the driver-side trailing arm, removing the nut and shims was fairly easy. The problem was that the pivot bolt, shown here, was frozen into place in the trailing-arm bushing.
24 While the pivot bolt wouldn’t budge, the shims would, so I was able to slip a Sawzall blade into the frame pocket, cut the bolt on either side of the trailing arm, and then remove it.
25 Make sure you lay the shims aside so you remember which ones went where; this will be important for reassembly. While not evident in this photo, the trailing-arm bushings were absolutely shot.
26 Out at last. Other than boxing them up and shipping them to Van Steel for bearing rebuilding, this is the last we’ll see of the factory trailing arms.
27 The new coilover trailing arms from Van Steel, fully assembled and ready to bolt in. It almost seems a shame to put something this pretty underneath a car.
28 While the factory trailing arm was made from folded-and-welded steel, the Van Steel arms are of much thicker stock, with welded reinforcing ribs down the inboard side.
29 Another portent of things to come: one of the adjustable coilover shocks that will go in with the new trailing arms. Stay tuned. vette
Check out the rest of the series in Part 1
and Part 3
of the Sure-Footed Shark!