1940 Ford Front Wishbone - Bone Of Contention

Splitting the wishbone means the spring perches will no longer be perpendicular to the centerline of the car. The final step in prepping the 'bones was to tweak the perches to correct their angle. Using heat and a monkey wrench the perches were twisted slightly...

...the exact angle determined using this temporary jig Frank had constructed. Knowing the new angle between the wishbone and the centerline of the car meant he could clamp the 'bone in the jig and measure fore and aft from a straight edge placed against the perch.

Whether they'd taken a hit sometime over the years or whether they came from the factory like this, who knows, but the perches weren't exactly parallel with each other, as demonstrated by clamping them in a vice and observing the different angles of the 'bones. Yes, that's the Rolling Rice Bowl dragster behind, in the shop for some remedial steering box work. Good company indeed!

While Frank applied heat, Nate pulled down on one of the 'bones until a level placed across the two of them indicated they were identical.

Here's the new Speedway Motors Model A spring that we used, compared to a stock A spring. Note how the original has sagged somewhat during its 80-year lifespan. I'm hoping with two fewer leaves than the stock spring, the Speedway version will provide a softer ride, especially as the finished car will be lightweight.

With the Speedway spring clamped into the rear crossmember, Nate used a leafspring spreader to spread it from 39-42 inches. This puts it under tension so once the wishbones are mounted and there's weight on the car, the shackles remain at less than a 45-degree angle. If the spring were not spread like this, and just bolted into place, when there's weight on the car, the spring would spread and the shackles would likely end up vertical, allowing the rearend to move side-to-side, requiring a Panhard rod and resulting in poor suspension action.

With the spring spreader still in place (it isn't removed until the very end of the job) the wishbone was connected to the spring using early Ford rear spring shackles, which measure 2 1/4 inches wide. Unfortunately, front springs, and hence front spring hangers, such as those on the '40 'bones, measure 2 inches wide. We used washers to make up the 1/4-inch difference for now, but will machine up a 1/4-inch spacer before the car hits the road. The spring and wishbone assembly (not to mention the rear of the chassis!) was supported on blocks of wood.

The front ends of the 'bones were to be mounted next. The spring dictates the height from the ground of the rear of the 'bones, and we wanted them parallel with the chassis 'rails for appearance. This meant the tie-rod ends used at the front had to be mounted in tapered holes a distance of 4 1/2 inches from the lower edge of the 'rails. This chassis will get Z'd at a later date with the 'bones mounted through the sides of the 'rails, so we were going to fabricate temporary mounts, until I remembered Jimmy White at Circle City Hot Rods had made these cool mounts for a customer's car and never used them. As luck would have it they fit our measurements, so I "borrowed" them for this story. Thanks, buddy!

With the brackets clamped to the chassis to ensure they were vertical, and placed in the same position on each chassis 'rail, Nate tack-welded them in place. Note the tie-rod ends had already been adjusted identically, and diagonal measurements taken to ensure the assembly was square in the chassis, as the spring can be clamped into the crossmember crooked. Ours was 3/8-inch out of alignment until we took measurements at this stage!

With the 'bones and spring located, it was time to mount the axle to the 'bones. Using a large square as shown, diagonal measurements were taken to ensure the rearend was square in the chassis. It was also measured to ensure it was central.

It's difficult to see, but with everything set up to start mounting the axle, we had a rethink when we realized there was less than 2 inches between the chassis and rearend housing. Sure, it'll be a light car, but I like to see at least 4 inches of suspension travel.

We mentioned that the chassis tables at Aldana Race Cars had other projects on them, and thought it'd be interesting to see one of them, especially as it also uses split front wishbones to locate the axle. This chassis uses a banjo axle with integral spring mounts, and a reverse-eye reshaped Model A spring. The 'bones don't carry the spring, and attach via four long plates sandwiching the axle bracket. The chassis is heavily Z'd and fully boxed.

We succeeded in finding the extra travel by moving the axle forward and down into the curve of the dogleg on the 'bones, leaving an 1/8-inch gap between them. Sure this will alter the wheelbase, but we'd already altered it by putting the spring behind the axle in a Model A chassis, so another inch or so made no difference. Lowering the axle will also raise the rear slightly from our planned height, but as mentioned we'll Z the chassis later anyway.

Raising the axle meant taking all our measurements again, and as we weren't using a chassis table, plenty of measurements to check the chassis was level side to side, as well as the axle. The axle is level, central, and has had the pinion angle set at 5 degrees here, and the chassis is set level using adjustable jackstands. As mentioned, Aldana Race Cars' chassis tables were all in use, but I prefer doing it this way, as this is how most of you will do it too!

Here's how we mounted the axle to the 'bones, using commercially available curved welding tabs fore and aft of the axle, as well as either side of the weld where the wishbone tube joins the cast-end section.

While function is the primary concern when fabricating suspension parts, on an open-wheeled hot rod, form plays an important role too. Not only did we want the 'bones running parallel with the chassis when viewed from the side, but we also wanted them parallel when seen from above.

Once I got the chassis home and mocked up on wheels, I got to thinking about side loads imposed on the axle mounting brackets during suspension movement. To combat any sideways loads rotating around the mounting points, as they're higher than the spring perches, I'll add a couple of tabs between the axle and wishbone as shown. I'm no engineer, and they may not be needed, but as this will be my fiancèe's car, I'll feel happier with them there.

With the rearend mounted, this side shot gives a good idea of the altered wheelbase. The rearend has come forward 7 inches from the stock location directly under the rear crossmember. The chassis is mocked up here with a front axle that mounts in front of the spring, pushing the frontend out 5 inches, which almost restores the wheelbase to stock dimensions, though obviously it won't work with a stock body!