If someone on this thread has installed a PS box and has a SW that’s off center, then this might help. However, it may not apply to the off center SW problem the OP is experiencing.
I installed a 1974 PS gear box on my 1965 C10 frame. It’s a common upgrade and I used a professionally made adapter plate to make it fit properly.
The first thing I noticed was that my SW was off center. (Since the pitman arm is splined with a flat spot, it can only be installed in one position. No adjustment possible.)
So I centered my SW so it was straight when driving straight.
Next problem I noticed was that I had fewer SW turns to the LEFT than turns to the RIGHT.
Here’s why.
The PS box adapter plate sets the PS box off the frame about 3/8” from where the factory gear box was. So that means the CENTERED pitman arm now has the CENTER LINK off center to the LEFT by 3/8”. This means the tires are now in a slight right hand turn when the PS box is centered. To compensate for this and point the tires straight, the driver needs to turn the SW to the left slightly. So now, the steering box is no longer centered when driving straight ahead.
This explains why the SW was off center and why I lost about 3/4 turn of the SW to the left.
To correct the matter, I had to adjust the tie rods with the pitman arm centered. In my case, the DS tie rods were adjusted shorter and the PS adjusted longer so the end result had my tires pointing straight again. I made sure my SW turns left and right of center were the same. I then checked alignment. Last, I centered the SW.
I hope this helps someone.
