In 1962, Ford had a perfectly okay LCA setup for the fullsize models. Double A-arm, caster and camber adjust at the top A-arm, leading steer. Nothing horribly deranged - that had to change...
The arms are tilted forward, making the setup leading-arm style, which is good thinking, mostly. Torque transfer under braking fights dive, etc. etc. But it wasn’t complicated enough. See, if you’re braking at low speed, the toe-in can change slightly, making it resist turning off-straight a little bit, and when experiencing a one-wheel bump, the setup sees some bump-steer. Neither is too good for unassisted steering, which was still standard. WE MUST FIX THIS FOR GRANDMAS AND THE CHILDRENS. AND THE ‘63 MODEL YEAR.
Most people would put in a steering stabilizer or redesign the linkage geometry. Is that what happened? Is that balls. No, Ford decided that the suspension needed to move around more. Wait, that’s not a solution. That’s idiotic.
The “solution” was to make a much larger boss through the frame and install the bolt system visible at the top of this post. A tiny little crank, allowing the front end of the LCA to travel inward and outward based on the balance of forces, a limited amount. I’m still puzzling out elements of this, but I think it’s something like this:
The LCA is a trapezoid of force, spring pushing down, spindle and frame mounts pulling back up. Think of it as a finger pushing down on a wobbly four-sided die. The neutral position (held in tension by the steering link, etc.) is with the “crank” slightly inward and down. When a bump hits (green), a normal A-arm would pivot and compress the suspension, but with this, something else happens first. The trapezoid “tilts” around the spring, and the crank goes down and out, causing the instantaneous caster, camber, and toe-in on that side *all* to change, and muting the instant movement transferred to the shock.
The wheel will tend to begin to dodge away from the hole, i.e. bump steer - but before it’s done bump-steering, the crank swings back the other way, past its neutral position, which would cause the bump-steer to get canceled.
Summary: worse instantaneous bump steer, but lessened shock to the car, and the bump-steer cancels itself out after a drunken swing. Ford, WHAT THE FUCK.
In cornering, the outer wheel will tend to try to push in, and the inner wheel will try to pull out. For that, the Ford MoronoCrank System also has you covered.
Under normal steering (left turn, red line pittman position) the inward push of the right A-arm and outward extension of the left A-arm works okay - toe relation, relative angle change, all pretty consistent between the two sides, and as a plus, the wheels have actually changed position to improve their alignment to the turning radius. Neat.
This all changes if you’re braking hard. As the car shifts from neutral position to a right turn while braking, the arms can shift the same way as a neutral/accelerating left turn, and the left wheel “digs in” - SHARPLY (green linkage). The right wheel (inside), actually doesn’t do much. This makes manual steering much easier, because the outside wheel is getting “assisted”. However, at speed, this is... REALLY DANGEROUS, because it’s a recipe for the car swinging back and forth depending on how much the instant wheel drag is pulling on the suspension.
As a side note, the system does have a fringe benefit that I discovered by accident. If your brakes aren’t working right and one wheel locks up, it will *not* pull the car out of a straight line, particularly.
So, what happened?
Well, as it turns out, this system, being completely undamped and really sensitive to weight shifts was a *REALLY* bad idea for big-block cars and less than a great idea for ordinary cars. Lurching back and forth at speed, wobbling while under braking, and otherwise being terrifying - plus, it wears out the front LCA bushing like a mofo (angle is always changing) *AND* likes to work loose. Huzzah.
Ford were aware of this. They offered for performance models and cop cars/taxis a bar which would tie the two cranks together. Not a straight bolt system, because that would make too much sense. Very soon, several aftermarket bars also showed up, along with kits to replace with straight bolts (and not cranks). Moog offered a rubber-bushed brace instead of the bar, which located the crank to the front crossmember. Some people even welded the cranks in place.
So, what’s the best solution? If you like the car to feel as much as possible like a waterbed (and who doesn’t!), then you need to rebuild the offset shafts. This is a pain, because the offset shafts were only on cars ‘63-’64, and in ‘65 they changed the suspension completely. They are greasable, but most are worn out, and replacements are limited and expensive.
The straight shaft conversion of original style bushings and the Rare Parts offset straight shaft are both insanely expensive as well. (Typically >$300) There is an adjustable cross-bar available for ~$100 and a non-adjustable for more like $70 - both will preserve a *little bit* of factory design wobble and will reduce wear, but they require the original system to be in place.
So, what drove me to research all this? The fact that my ‘63 is loose on the left front and slapping like a sumo wrestler’s little sister. Obviously.
Ford: designing suspensions systems that wobble on purpose and try to kill you since about drunk o’clock this morning.