i disagree.. Triangulated 4 linkset ups work just as well if not better than parralell 4 links w/
panhard bars..the issue is. ford designed the 4 link to be produce 5 millions times, be smooth and ride well for the DD..
From a dynamics engineering perspective, triangulated 4 links are about the worst thing on the planet. They are, by necessity, full of compromises and they aren't particularly good at
any one thing. Because the bushings have to be necessarily soft, the axle is all over the place in back and good drivers can feel this. The only rationale for using them is that they're cheap. Ford engineers were able to tune bushing durometers, for a decent ride for what the Mustang really was, a mass-market grocery getter with sporting pretensions. The need for quad-shocks should be enough to indicate that there is a
lot of compliance
required by that design and compliance doesn't equate to a "good"
suspension. And the problem is that you can't just stiffen up the bushings to get better axle control without introducing binding and even risking the health of the torque-boxes, and you never get away from the terrible geometry changes the topology exhibits as the
suspension is moved through its range of travel.
You're right that it's an okay (read "cheap")
suspension for mass production and has been tuned to provide a reasonable ride but when lots of power is put to it or the driver has expectations that include track time, the 4-link needs help.
I still think that if one wants to use a live axle, a torque-arm/
panhard (or better yet a Watts link) setup is the best way to decouple axle reaction and location management tasks. Even Ford did this with the S197.
plus the worst thing about the factory 4 link is the weak UCAs and
LCA's.
I don't think the arms are that bad (in fact, if you've seen the episode of
Mythbusters where the guys try to rip the rear axle out of a Crown Vic like was done to that cop car in
American Graffiti, you'd remember that the axle didn't come out without removing bolts and significantly weakening the
control arms with a cutting torch and even then it didn't completely separate from the car...) though for aggressive driving, boxing them might help. But any stiffening of members like the
control arms will always be offset by slop in the bushings necessary for this design.
The factory bushings in the front location of the
lower control arms allow for lateral, axial and rotational deflection to accomodate the needs of the
suspension as it moves. Putting spherical bearings there removes at least two of these degrees of freedom. If you're doing a road course car and you've set the
suspension up very stiff and for very limited travel and body roll, this is probably acceptable. But for a daily driver that sees frost-heaved roads and potholes, removing these degrees of freedom while still expecting stock or near-stock
suspension excursions will probably result in cracked sheetmetal at the chassis mounts. I wouldn't even put PU bushings in the front for this reason.
....busted!!!
Oh don't get all
You're gonna get 
from time to time around these parts
