If you drag race your car, you need not read any further.... the stock style 4 link will be fine.
I totally disagree with their use, here's why. A general rule of suspensions is that they should not bind anywhere through their operation. The car should only depend on springs shocks, and anti sway bars to control vehicle movement not the binding of suspension pieces. Ford decided to blow that idea off with the design of the upper control arms that connect the stick axle rears to out cars. They serve two purposes (actually 3) 1. they locate the axle, fore and aft, 2. they center the rear in the car and 3. impact the pinion angle (which is important but not really part of this discussion).
The lower bars are parallel and not much of an issues (although their geometry can be improved by relocation their major contribution is to locate the axle fore and aft) If you improve the bushings or the stiffness of the lower bars you may see an improvement in handling because they force the upper bars to react in a less positive manner.
In any case, these upper bars are designed to oppose each other in order to locate the rear side to side.
So picture this, the car is set at "engineered height" (where Ford wanted it to begin with, wheel gaps and all) the suspension in unbound the rear is centered in the car, all is well.
Then we lower the car and the suspension is immediately in bind because we have gone away from our "engineered height". The upper bars are now fighting each other and stress is placed on those bushings. Now you can use adjustable upper arms to fix the height issue but it will only be fixed with the car at the desired ride height, as soon as the car's suspension moves, it is already binding up. What usually happens at this point is that as the upper control arms attempt to force each other into compliance (by centering the rearend) . the driver feels this as a condition of "snap oversteer" where the rear axle tries to unbind and center itself on corner exit.
Now, and I've done this myself, and am trying to save you guys the painful experience, if you install a panhard bar it is really the only thing operating as designed in a decent suspension set up. You can set the bar at the correct car height, but you still have to deal with the bound up upper arms, what is worse, you have now introduced ANOTHER arc into the suspension geometry that induces bind. If you set the car up like this you can twist on the PHB, and instead of the rear locating in the chassis you will push one side of the car up into the air, adding ride height to the right side of the car (using an MM PHB that locates on the right side of the body. (it will also locate the rear but only secondary to raising the car body). This is because it is fighting the arcs of the upper control arms, it is the upper arms that are creating the problem. Using anything to stiffen the upper arms, including the roller ball-type bushings in the rearend housing just makes this worse, although, it would seem that those bushings with soft upper control arm bushings do seem to help.
The short answer is to use the upper arms from a car that has the oblong bushings in order to force them into compliance, feel free to dip the rubber ends in some type of rubber softener as well. I used to do this on my autocross car when I was forced to use the the stock suspension because of the rules. You may even get away with using a PHB, but those upper bushings need to be compliant, and they won't last very long because they will still need to locate the rear fore and aft. It sounds just the opposite of what we have all been told, stiff suspension bushings help handling..but not this time.
The cheap, fast and effective way to fix this is to undo one of the upper control arms and use a PHB, if you have the nuts to do this you will be surprised how well the car handles, the problem, other than you will eventually rip the one upper control arm out of it's brackets is that you are still dealing with it's arc, but to a much lesser degree. It only has to locate the rear fore and aft, no longer side to side. ( it's not fighting the other arm to center the rearend, it's relying on the PHB to do that) You can actually install a decent fabricated upper arm, complete with heims for this.
The other fixes range from an IRS (which has it's own issues, including weight) Watts linkage, or the truck arm style suspension or to fabricate a single center upper mount and arm, (back in the day somebody made a kit for that but it impacted the back seat.) A Jacob's ladder might also work and it is very light, but it would take a lot of fabrication and may not hold up under extreme handling.
The problem is with the upper control arms and their opposing arcs, the PHB will just add another, competing arc to those that already locate the rearend in the car. Get rid of those upper arms and your problems are basically solved.
I totally disagree with their use, here's why. A general rule of suspensions is that they should not bind anywhere through their operation. The car should only depend on springs shocks, and anti sway bars to control vehicle movement not the binding of suspension pieces. Ford decided to blow that idea off with the design of the upper control arms that connect the stick axle rears to out cars. They serve two purposes (actually 3) 1. they locate the axle, fore and aft, 2. they center the rear in the car and 3. impact the pinion angle (which is important but not really part of this discussion).
The lower bars are parallel and not much of an issues (although their geometry can be improved by relocation their major contribution is to locate the axle fore and aft) If you improve the bushings or the stiffness of the lower bars you may see an improvement in handling because they force the upper bars to react in a less positive manner.
In any case, these upper bars are designed to oppose each other in order to locate the rear side to side.
So picture this, the car is set at "engineered height" (where Ford wanted it to begin with, wheel gaps and all) the suspension in unbound the rear is centered in the car, all is well.
Then we lower the car and the suspension is immediately in bind because we have gone away from our "engineered height". The upper bars are now fighting each other and stress is placed on those bushings. Now you can use adjustable upper arms to fix the height issue but it will only be fixed with the car at the desired ride height, as soon as the car's suspension moves, it is already binding up. What usually happens at this point is that as the upper control arms attempt to force each other into compliance (by centering the rearend) . the driver feels this as a condition of "snap oversteer" where the rear axle tries to unbind and center itself on corner exit.
Now, and I've done this myself, and am trying to save you guys the painful experience, if you install a panhard bar it is really the only thing operating as designed in a decent suspension set up. You can set the bar at the correct car height, but you still have to deal with the bound up upper arms, what is worse, you have now introduced ANOTHER arc into the suspension geometry that induces bind. If you set the car up like this you can twist on the PHB, and instead of the rear locating in the chassis you will push one side of the car up into the air, adding ride height to the right side of the car (using an MM PHB that locates on the right side of the body. (it will also locate the rear but only secondary to raising the car body). This is because it is fighting the arcs of the upper control arms, it is the upper arms that are creating the problem. Using anything to stiffen the upper arms, including the roller ball-type bushings in the rearend housing just makes this worse, although, it would seem that those bushings with soft upper control arm bushings do seem to help.
The short answer is to use the upper arms from a car that has the oblong bushings in order to force them into compliance, feel free to dip the rubber ends in some type of rubber softener as well. I used to do this on my autocross car when I was forced to use the the stock suspension because of the rules. You may even get away with using a PHB, but those upper bushings need to be compliant, and they won't last very long because they will still need to locate the rear fore and aft. It sounds just the opposite of what we have all been told, stiff suspension bushings help handling..but not this time.
The cheap, fast and effective way to fix this is to undo one of the upper control arms and use a PHB, if you have the nuts to do this you will be surprised how well the car handles, the problem, other than you will eventually rip the one upper control arm out of it's brackets is that you are still dealing with it's arc, but to a much lesser degree. It only has to locate the rear fore and aft, no longer side to side. ( it's not fighting the other arm to center the rearend, it's relying on the PHB to do that) You can actually install a decent fabricated upper arm, complete with heims for this.
The other fixes range from an IRS (which has it's own issues, including weight) Watts linkage, or the truck arm style suspension or to fabricate a single center upper mount and arm, (back in the day somebody made a kit for that but it impacted the back seat.) A Jacob's ladder might also work and it is very light, but it would take a lot of fabrication and may not hold up under extreme handling.
The problem is with the upper control arms and their opposing arcs, the PHB will just add another, competing arc to those that already locate the rearend in the car. Get rid of those upper arms and your problems are basically solved.
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