We got off topic a little here. The spherical bearings we are talking about are in regards to the two rear upper links that connect the axle to the body. The shock mounts shouldn’t cause binding unless they were excessively hard.
The rear suspension on the SAAB is basically like a 4 link, except with the upper link facing to the rear. In roundy round talk they call this a Z-link. It’s basically a variation off a Watt’s linkage. Like this:
http://www.brockeng.com/mechanism/Watt.htm
The point of the upper links is straighten the arc of the axle as it goes up so that the wheel is moving basically straight up and down and thus wheel travel does not have an effect of moving the axle in position front to rear thereby creating an unwanted rear steering effect (bump steer). This works all fine and dandy if all the arms in the linkage have the same dimensions. But Saab had some space contraints to work around so they couldn’t pull off a geometrically perfect watts link. The result is that a slight amount of rear steer is built into the system, not a huge issue and our cars certainly have less rear steer than most cars of the period that had simple single pivot trailing arm based rear suspension systems. No problem here.
There is no binding as long as both of the rear wheels are working in tandem, going up and down at the same time. The problems arise when the rear suspension tries to work independently. One wheel goes up which will cause the rear axle to twist slightly as the upper links try to straighten the arc out. Look at the animation and imagine if the center point (P) were hard fixed (as it in a saab) to the bracket that comprises points B and C. You can see that P would rotate slightly as it went up and down. But say the other wheel wants to go down at the same time. As it lowers the linkage does its thing and keeps the axle in a straightish plane, rotating the axle on its centerline to do so…but in the opposite direction! The axle can’t twist in two directions at once so the result is that the suspension locks up, binds. In a case like this most likely the side with more force being applied to it will win out and force the other side to move in a similar direction.
This phenonenom is eliminated in most race car setups by a device known as a birdcage. A birdcage is a bracket that contains the upper and lower links for the 4 bar suspension but with a large bearing where it mounts to the axle instead of being welded. This allows the suspension to stroke freely on both sides without bind but it also over complicates it because now the brake ears have to be mounted to the 4 link brackets and not the now freely rotating axle. For a rear drive car the axle still needs to be restrained from spinning around so another stabalizing link is added from the diff going foward.
Now heres the thing... The saab system is a modified watts link which allows some rear steer but also eliminates some of the twisting effect that can cause bind. Combined will all the rubber bushings back there, there is more than enough play to prevent any binding effect. I jacked up my car and removed the shocks and springs on one side. Then the burly 140 lbs of of me lifted one side of the axle from full droop to bump stop without any sign of bind up. This is with red poly bushings in the upper links.
Now for some more anecdotes:
I had a saab once that had really worn out upper bushing and allows a lot of play. It handled horribly! The turn in was super slow and in linked corners the loading/unloading of the rear suspension made the car very unpredictable. When I replaced with new ones the car became crisp and predictable at the limit.
So heres my theory and what I am going to try. I'm going to go ahead and make up upper links with spherical bearings at both ends and mount them on the car. I think that there is enough slop built into the other mounts in the suspension to prevent binding and the increased predictability of the rear will be worth it. Besides its a front wheel drive can and the point of the rear wheels is just to keep the muffler from dragging after all, right? They are easy enough to change so maybe we can swap them around at service and get some driving impressions on stage of the two setups.