Its been done.  To do it correctly you need a Watts linkage or panhard rod though, so its really more like a 5 link.  Some guys have angled the upper arms to try and eliminate the 5th link like a Fox Mustang, but I can tell you those system always bind and can create unpredictable handling. 

I think most just feel its too expensive and unnecessarily complicated.  Good springs and shocks have always been sufficient for me.
 

I can’t say I have suffered with my 5 leaf mid-eye springs.

It’s the shocks and rear sway bar that caused a firm ride.
The shocks are too stiff for washboard/potholed roads.
The rear sway bar has since been removed due to oversteer.

On the front, the performance shocks and springs, the harshness was primarily from the front shocks.
That has been remedied by the use of coil overs (350# springs).

Last edited by Nos681 (3/12/2022 9:04 PM)

Bearing Bob wrote:

TKOPerformance wrote:

Some guys have angled the upper arms to try and eliminate the 5th link like a Fox Mustang, but I can tell you those system always bind and can create unpredictable handling. 

I think most just feel its too expensive and unnecessarily complicated. 
 

 
Always is probably not the correct word to use. I've got rod ends with spacers between the mounting brackets, on the ends of my control arms on my triangulated rear suspension without bind. I removed the springs from the shocks and moved the axle thru its range of movement, and I could rotate the control a bit at each extreme.

You can make the ride too soft or too hard if inclined. I prefer a soft spring and fine tune with the shock. On Bash trips where I'm loaded to the gills, I use a stiffer rear spring and a firmer shock setting. I've got less than $1k in the rear suspension. One thing about my suspension is that it's very predictable and neutral.

As usual BBII very nice work!  As always, your mileage may vary, but here's what I've discovered/experienced with triangulated 4 link rear suspensions:

The bind won't show up by just removing the springs and cycling the suspension.  The problem is that's not how the suspension is loaded during hard cornering.  Initially we did that with the Fox cars too.  Everything seemed to work, and we couldn't understand why near the limit the back end would immediately come around with no warning.  We lacked the ability and technology to figure it out, but years later talking with the guys from Maximum Motorsports and Griggs it became evident that what was happening was that we hadn't accounted for what happens when the axle tries to move to the outside of the turn under high cornering loads.  Basically it was deforming the bushings so much that they bound and when the suspension could no longer move upward the tires broke loose causing a skid.  The addition of a panhard rod solved the problem effectively for 90% of people.  The other 10% needed a torque arm system with no upper arms. 

So, granted, this is under racing conditions, but speaking from my own experience I stand by my original statement.  A triangulated 4 link works fine for the street and drag racing, but the more serious you get about handling on a track the more glaring the inherent issues become.  Better geometry than Ford used in the Fox cars may improve the situation, but in the end the arcs the upper and lower arms travel are different because they are not parallel and different lengths.  You can get them closer like changing the tie rod angle in a front suspension to improve bump steer, but the length difference and angle difference are impossible to completely nullify. 

I'll add that also owning a 3rd gen F car one thing GM definitely got very right on those cars was the rear suspension.  The Mustang looked better, was faster, and I generally like it a lot more than the F-car, but the F-car was a lot more confidence inspiring to drive fast on twisty roads. 

Last edited by TKOPerformance (3/13/2022 3:47 PM)

Not currently. But with the fmx and aod I had a very slight oscillating vibration that I could feel in the steering wheel, gas pedal and seat. With the top loader now there is no vibration. I would like the drop the car at least an inch, but I'm afraid of. getting another vibration.

Last edited by Bearing Bob (3/13/2022 6:50 PM)

MS wrote:

I have just never seen the need to change to something different, although I am sure it would be fun to do so. Maybe even get rid of some bad vibes.

How is that adjustable rear camber on your car coming along, BbII? Are the wheel bearings doing ok?

Bottom line: I don’t have much issue with stockish suspensions acting like they were designed to act, with addition of modern valved shocks snd stiffer springs. I will
Make this statement: That bone stock 66 six cylinder convertible I just bought rides 100% better than any other Mustang I have ever owned. It is like driving a normal car!!! (Braking not included)

You better swap that suspension on your fastback!...;)