When I bought my car 2 ½ years ago, the springs had been replaced about 10 years prior. It was a cobbled together assembly, using 62 pads with 61 pad retainers, a very poor fit. The springs were sagging (perhaps due to minimal use of the car). As part of an all around spring and shock replacement at that time, I replaced the rear springs with new ones from Eaton Detroit Spring. They offered me the option of the springs for the convertible vs the hardtop, 1200 lb capacity vs 1000 lb. I chose the stiffer springs and used 61-type pads from one of the TBird vendors. It was obvious that the 61 pad was less substantial but I assumed the 61-type pads were not available at the time of the earlier replacement.
After reading about Ozzy351's successful effort to convert his 61 to the 62/63-type rear spring pads, I contacted him concerning a source for the beefier 61/62 pad retainers. I purchased a used set (Bird Nest). Powder coated were not available so I had them media blasted and painted them myself. Realizing that this mod would tend to lower the rear of the car and wishing to raise the rear a bit, if possible, I chose to install new, 2” X 3” X 1/4” X 4” long sections of mild steel rectangular tubing above the rear, rear spring brackets.
Having replaced the springs and pads before, the effort was less “intense.” The shop manual was helpful. My advice to anyone attempting this for the first time is to have a mind to safety throughout. The frame as well as the rear axle must be supported, independently. A bottle jack was helpful when I needed to jack the springs into place under the axle but care must be taken so as not to lift the frame of the car.
I re-used my fairly new rear springs. The 62/63 spring pack is joined together with a 3/8” high strength bolt with steel spacers at top and bottom that fit into recesses in the spring pads. They look similar to a stovepipe hat. After finding the dimensions in this forum (thanks Plowell), I had the spacers fabricated by a machinist friend for a 5/16” bolt so as to fit my 61 springs. Longer 5/16” grade 8 bolts were used.
I re-used my old spring clip plates. Since the 62-63 pad retainers are wider than the 61's, this required elongating the U-bolt holes in the plates. A better option might be to locate 62/63 spring clips. I used heavy flat washers on the U-bolts, trimming the sides as required to fit inside the down-turn of the spring clip plates.
The center hole in both the spring clips and box brackets on the underside of the axle had to be enlarged from 1” to 1-1/2” to accommodate the 62/63 pad retainers. My machinist friend enlarged the hole in the spring clips. I used a die grinder with 3/8” double-cut carbide bit to enlarge the holes in the axle brackets. This was a little tricky but do-able with some care to make sure the enlarged holes were centered on the old ones. Safety goggles and a face shield are a must. Metal chips!
One side of the pads did not “squish” as much as the other, apparently due to slight differences in pad retainer inside height. The first trial demonstrated some loose feeling in the rear end but this was corrected when I torqued the spring shackle nuts and spring U-bolts to the shop manual specs.
Measuring at the center of the wheel, vertically to the inside curve of the wheel well my car's dimensions were/are:
Spec (1963 - TBird Ranch) Front 27” Rear 20-1/2”
Before the mod (after spring and shock replacement) Front 28-1/2” Rear 22”
After the mod Front 28-1/2” Rear 22-1/2”
My wheels are 15” with 225-70 radial tires. By my calcs, this combination results in a diameter very near that of the original wheels and tires.
Here are some pictures from my work.
Old parts.
New/old parts before installation.
More new/old parts.
Rear of spring, not raised yet.
Spring at axle, not raised yet.
Rear of spring, in place.
Spring at axle, in place.
New stance. Well, not much different than the old one. The floor is just about level. I am happy with it. The rear shackle is just visible beyond the muffler.
Thanks Ozzy351 for putting up with my emails. You were great.
Bill