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Road Runner Chassis Restoration Part 2

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by Huw Evans  More from Author

Finishing our budget upgrades.

1968 Road Runner In the first installment of our 1968 Road Runner undercarriage detailing, the folks at Legendary Motor Car had gone through our classic B-body and started removing the entire suspension, driveline, brakes, and fuel system, getting it ready for restoration. Although the car looked fairly presentable underneath, the more we investigated, the more we realized that it actually needed quite a bit of work in order to achieve the factory look we were aiming for. In addition to the incorrectly painted parts, some items showed signs of rust and wear and would need to be cleaned and repaired. As is often the case with restoration projects like this, there was more work actually required than we originally envisioned. But a saving grace was this particular car’s largely rust-free condition. Many of the original chassis components could simply be cleaned and reused, which as you’ll see ultimately saved us quite a lot of money whilst achieving some very satisfying results. Follow along to see how.

In order to get our 1968 Road Runner’s unibody ready for paint, we’ll need to carefully dry sand the entire underneath, removing any spots of under coating, along with the old SS1 Yellow exterior color. When it comes to painting, preparation is everything. We used 40-grit paper for initial sanding, followed by 80 and then 180 to remove any remaining rough areas of paint and undercoating. A Dremel tool removed any traces of rust, particularly in small areas. In order to prep the underside correctly, the process will take several full days.

Remember the car’s original 8 ¾-inch rearend from last time? In order to begin refurbishment, the axles were pulled. Its fluid must be drained and then the differential needs to be cleaned and inspected.

The differential is washed using automotive solvent cleaner. We discovered that the diff was in good shape, having been regularly serviced. However, we also noted that it is a 3-series 742 open rear, not a Sure Grip as indicated on the car’s build sheet. Furthermore, the part numbers indicate that this is the original unit installed at the assembly plant in Lynch Road.  

The empty rearend housing was then cleaned and sanded to remove the old, heavy paint. Now that it’s back to bare metal, it’s ready for a fresh coat. Although we used a downdraft spray booth, you can do this at home in the garage, though make sure you have a sturdy support to hang the housing on while painting. As for the finish, any good quality automotive paint will do–and make it black for an original look.

One place where you can save a ton of money on cars like this concerns the rear leaf springs. As long as the car doesn’t display high mileage or seriously worn springs, the existing ones can be restored. Since ours were in good shape, despite being coated in surface rust, we did not need to purchase replacements. The springs needed to be stripped, cleaned, painted, and re-assembled. We opted to coat them in natural steel paint, which preserves the original look and prevents them from rusting within a few short months. New bushings and metal spring retainers were the only replacement parts needed. Our old springs now look brand new.

Moving on to the front suspension, the car’s original upper and lower control arms, torsion bar springs, and sway bar all need to be sandblasted and restored. The control arms were not only rusted, but also covered in thick black paint (they should be natural metal). Because the paint was so thick, it took several hours to remove most of it, using automotive solvent and a scraper before we could sandblast the parts.

 Besides the suspension, somewhere in this car’s past the A883 transmission casing had also been painted–the main part aluminum and the tailshaft black (the casing should be natural metal/cast iron). Since this is also not correct, once the fluid had been drained we needed to clean the housing and remove the old paint, using plenty of degreaser, followed by solvent and a brush.

For that factory-correct look we also needed to remove, clean, and re-finish the transmission casing bolts using a special chemical compound, which blackens them, replicating the OE appearance. For you do-it-yourselfers, The Eastwood Company offers a special metal blackening kit for around $40 that includes all the tools you need. In our case the biggest issue was getting the bolts out, since the two Allen pieces on the left side of the casing proved very difficult to remove, requiring a lot of heat penetration to loosen them.  

Once the bolts and shift linkage had been pulled off, the old paint stripped, and the holes and tailshaft end masked, the transmission casing could now be painted. In order to replicate the natural metal finish but prevent premature rusting, we elected to paint the casing using a cast-iron automotive paint. Again, sources like The Eastwood Company are a great place for quality, OE-type automotive paint. With the refinished “blackened” bolts in place and the shift linkage reinstalled, the result speaks for itself.

Getting back to the underbody, we’re just about ready for paint. However, for the best possible result we need to remove the black rubber grommets that cover the drainage holes in the floor and trunklid, and mask the holes with tape to prevent overspray. This also requires removing the spare tire and trunk mat.

This next step is easy to do yourself, though make sure you have adequate ventilation. To replicate the original underside finish, it was necessary to spray the floorpans with gray, satin-finish acrylic urethane paint, which resembles the factory primer but is far more hard wearing. Next, we carefully mixed an acrylic urethane solution that matched the car’s SS1 Yellow exterior color, and carefully applied it over the gray to replicate the look of factory body paint overspray. It’s never been easier to achieve the correct, restored look.

Remember our sorry-looking upper control arms? Well here they are, along with the refurbished lowers, spindles, and end links. New bushings have been fitted, and the spindles and arms correctly color-coded. They’re now just about ready to go back on the car.

Besides the suspension components–which we were able to entirely re-use, save for the bushings and rear spring retainers–the same applied to the brakes. All we required were new lines, new cylinders for the front wheels, and fresh shoes. Here are the rear-drum backing plates, fresh from sandblasting and now ready for paint.

As the rest of the rearend assembly starts coming together, we can begin putting the differential back together. Here the cap bolts are properly torqued. Due to the design, we can actually install the rear axle on the car before attaching the differential unit.

It’s the details that really count. The original steering linkage and tie-rod ends, having been blasted and painted, were also re-installed. We were able to source the correct castle nuts that link the inner and outer tie rods to each other, and the spindle extensions as well.

Out back, with the rearend and leaf-sprung suspension back on the car, Legendary’s Jim Coleman reinstalls the axles. With the transmission also installed, next will come the driveshaft.

Items that can make or break an undercarriage detail are the gas tank and straps. If the original tank and straps are in good condition they can be cleaned and reused. If you opt for a replacement, companies like Classic Car Auto Parts offer them, along with replacement straps and even sending units. A complete new tank and hardware for one of these cars can be had for less than $400.

Our Road Runner is done. Note the cast-iron finish on the original drums and the “as-new quality” of the control arms, which contrast with the exterior paint. Also note the orange color on the lower arms–this is Cosmoline, a petroleum-based compound that is designed to prevent them from oxidizing. Chrysler applied an anti-rust compound to the car’s original bare metal arms–this replicates the factory look while improving longevity. The undercarriage now looks spectacular, and aside from materials this entire project cost us less than $1,500, including the cost of the exhaust, fuel tank, stainless fuel and brake lines, new brake wheel cylinders, master cylinder, and shoes!

Road Runner Chassis Restoration Part 1


Legendary Motor Car Company Ltd
8228 Fifth Line
Halton Hills
Ontario L7G 4S6

Classic Car Autoparts
34553 Chisholm Trail
Grand Rapids, MN 55744

The Eastwood Company
263 Shoemaker Road
Pottstown, PA 19464


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