borgerding

I recently purchased a polyurethane rear control arm bushing kit, (Prothane #7322), and am in the process of installing them on my 63 Cutlass.
I removed the old rubber bushings, and cleaned up the inside of the tubular housings.
The new kit came with a bushings with integral flange, steel spacers, and thrust washers.
My question is in regards to the fitment or orientation of the new bushings/thrust washers into the frontward end of the rear lower arm. (The end that receives the shims).


Its puzzling, but from what I can see, the right and left lower arms are identical? Each arm is symmetrical, so there's no bend or variation in the stamping that would differentiate them as Rt and Lft.
(See attached photos of the rear/lower arms with bushings installed).

First off, is this correct? did Oldsmobile use identical arms on this car?

Secondly, if they did use identical arms, my issue is that the internal "step" in the cylindrical housing is on the same side on each arm. (See photos). This means that the new bushings go in from the same side, and the thrust washer goes in the opposite side.
Per Prothane's Kit, the thick thrust washer goes on the opposite side as the bushing flange. Because the thrust washer is thick, this throws off the center line of the control arm where it attaches to the bracket.
It "kicks" each arm over to the same side. This, I fear will screw up the geometry of the rear suspension/differential?

I spoke with Prothane, and they seemed puzzled as well. They claim that they test installed this kit on the same model/yr car, (original owner, with original control arms), and everything fit fine?

Prothane thought that maybe my arms had been serviced before, and that new steel housings where installed, and perhaps someone pressed a housing in from the wrong side?
I removed a housing from one of the arms, but because the housing has 2 different diameters, this cannot be the case. You cant simply re-insert it from the opposite side, it doesn't fit.
They also thought that maybe someone replaced one of my arms with the wrong one? (Maybe I have two "Right Side" Control arms on my car?)

With the original old rubber bushings, it didn't seem to matter as there was no thrust washer.

If anyone has any insight into this, I would certainly appreciate it.

(Even if someone could just crawl under, their same car, to see if their arms are identical?)

Thanks,

joe_padavano

The arms are exactly the same and the bushings go in from the same side. The difference in suspension geometry is meaningless. Stop losing sleep over it.

More importantly, the four bar linkage actually twists the upper arms slightly as the car corners. The stock rubber bushings have enough "give" in them to accommodate this. Poly bushings do not and will cause the suspension to bind up. Either use the stock rubber bushings at the front end of the upper arms, or get the metal spherical ball joint style bushings for that location. Your ride quality will thank you.