1958 Rear Suspension

[simplyconnected]

I want to know more about this:

Well? Did you try running with the clappers empty?

Hi Dave, still waiting for the differential parts to arrive, so for now the differential is out of the car. I presume it will take another two weeks for the parts to be in my hands...

That was three months ago. It seems like every time we get close to an answer, the thread dies or it gets replaced by some other topic.

Our '58 Squarebird owners have been living with this forever. Many have noisy or broken linkage. Neither is acceptable, especially when there are alternatives.

With respect, I believe some owners get to a point where they are 'happy with the situation' and they never get back to let the rest of us know what they did. - Dave

[Frango100]

Hi Dave, yes i forgot to reply back on this. The clappers are empty now on my Bird. The suspension is now nicely soft, as i wanted it. I drove the Bird several times and a few hundred miles city and highway and i´m quite satisfied with it. For some strange reason the clappers are now more closed without the bolts then they where before with the bolts. I have no explanation for this. The only downside is that when i go over a traffic bump and the rear comes down, the clapper will close completely and a metal to metal noise is the result. I did glue the old hockey pucks in the clappers, but already lost one. Will have to find some other piece of rubber to put in there. But normally i go slowly over a bump, so won´t hear a thing.
Previously i almost couldn´t push the rear of the car down, while now it is realy free to move. I didn´t encounter any wheel hop or other ill side effect of this modification. I´m not a racer and most of the time i´m just cruising around, but once in a while i put the "pedal on the metal" and all behaves well.
The Bird is at the moment out of service with a leaking radiator,
a starter motor rebuild and a transmission service, but waiting for the parts to come in. The radiator i just got back with a new 4 row core.
Can´t wait to have it driving again.

[simplyconnected]

Thank You Frank, for getting back with this valuable information. A few things come to mind.
Did you replace your rear springs? This would set a new height to the rear of your Squarebird.

In my opinion, the reason you could not push the rear down with urethane in the clappers is because there was restriction of motion caused by the clappers. This caused the rear axle assembly to roll which transfers torque to the upper arms. That is bad because it caused so many upper arms to tear out of the frame. Rear end motion should be straight up and down in a linear motion. The parallelogram arms should have freedom to accomplish this throughout the full range.

Full extension of the axle should be limited by your shock absorber stroke, not clappers. I see NO good reason for the clappers whatsoever. Instead, I do see how they are a direct cause for damage to rear end parts. Honestly, if I had a '58 Squarebird, I would cut the back half of the clappers off so that the axle regains full freedom of motion.

The clappers do not offer any strength to the assembly and they should not determine the ride of your Squarebird. The ride is determined by your shock absorbers and springs. Clappers restrict motion by binding. Does that make sense to you? It sure does NOT to me. - Dave

[Frango100]

Yes, i did replace the springs with new springs from Carl. The springs which where on there where non original springs which i thought where the reason for the harsh ride. But even after changing the springs, the ride was still not what i expected. Even then i could hardly move the rear up and down by hand. When the suspension is at full stroke, the clappers are fully open and with the suspension against the bumpers, the clappers will be fully closed.
This reminds me that i have to change the exhaust system, since the axle is hitting the exhaust pipe before even reaching the stops.. And thinking about this, this is probably what is causing the metal to metal noise after going over a traffic bump and not the contact of one or both clapper halfs. Already thought it was strange that i didn´t see any paint damage on the clappers due to contact.
Regarding the axle roll, that will (must) continue to happen, since there is a difference in lenght of the upper and lower control arms.
The only reason i think the clappers are there is to reduce the change of wheel hop by reducing the axle roll with the rubber pucks. (my thoughts, but i can be wrong). Probably with soft rubber pucks you can still get a soft ride while reducing the axle roll, but you will put more strain to the upper and lower control arms, were the upper arm is the weaker part .

[Astrowing]

I think the axle always rolls some since it is a psuedo parallelogram with nothing fixed except length of upper and lower arms. The bottom bushing is compressed to try to roll the axle aft lifting up the ujoint . The top bushing does isolate the clappers when hitting a bump. I’m happy with the way way mine rides even on my one mile dirt road with washboard. I have original springs in my 58 though. It is way too complicated of a design in my opinion.

[simplyconnected]

I think the axle always rolls some since it is a psuedo parallelogram with nothing fixed except length of upper and lower arms...

Of course the assembly needs to roll and yes, the upper and lower arms are different lengths. So are your front suspension control arms.

The same geometry holds true in the front and rear suspensions. Because the arms are longer on the bottom, you can look at it sideways and visualize an arc that is formed throughout the range of motion (by design). On the front when turning a corner at speed, weight squats the outside wheel. This extra weight causes the tire to 'tuck in' at the top and 'dig in' at the bottom to hug the road.

But what happens in the front if I freeze the bottom ball joint? The spindle and arms would try to 'roll' about the urethane bushings. I'm sure you would say that 'something will break at the weakest point' which is exactly what is happening in the rear. The upper rear suspension arms either tear out of the sub frame or they break. 'For every action there is an equal and opposite reaction.'

And that is what I meant. If 'axle roll' cannot happen, it WILL happen at the farthest extension, which is at the point where the upper arms fasten to the frame.

Again, the clappers restrict or freeze the axle to the bottom pivot, preventing it from moving freely. This causes the other pivot points to not rotate.

It's a bad design all the way around, was quickly dropped by Ford and never adopted again. Blame rests squarely on Ford engineers because they approved the design, the tooling, the production and assembly. Just because parts fit, doesn't mean they work well. - Dave

[Astrowing]

Agree. It’s a bad design. The original upper arm bolts to frame showed galling evidence before I touched them. I had to clean up threads with tap and die so obviously the upper bolts are moving. The car shows less than 100k and The suspension won’t last another 100000 miles. The best long term fix is to convert to a leaf suspension.

[simplyconnected]

...The best long term fix is to convert to a leaf suspension.

You can. That works but try this first: Simply remove the contents of the clappers. They add nothing to the strength of the rear end assembly.

That single move will relieve the stress on your control arms and give freedom-of-motion to the whole assembly.

Every other coil spring rear end depends on the shock absorbers for the correct ride and extension limit. This is frustrating for me because I've had dozens of coil spring rear ends and none of them ever had mounting bolt or trailing arm issues.

Try it. As Pres. Trump says, 'What the 773H have you got to lose?' If you really don't like the move there are other alternatives. - Dave

[RustyNCa]

Agree. It’s a bad design. The original upper arm bolts to frame showed galling evidence before I touched them. I had to clean up threads with tap and die so obviously the upper bolts are moving. The car shows less than 100k and The suspension won’t last another 100000 miles. The best long term fix is to convert to a leaf suspension.

What about converting it to a triangulated four link or a centerdrive truck arm suspension? Like a Hot Rods to **** setup?

http://www.hotrodstohell.net/index.htm