A better understanding of how UCA's and shafts are assembled and work would help everyone...INCLUDING ME! Here's the facts that I know and herein lies my confusion. Hex end-caps have internal and external threads. The external ones appear to be much finer pitch. The bare UCA has internal fine threads that the end-caps screw into. If I remember right, the end-caps cannot screw all the way in until two flat surfaces touch. I think I remember that the threads peter-out before that. Beginnings and endings of threads are not precise so when the end-cap external threads start getting shallower, you just can't tighten it any farther. That does not establish an exact finished location.
Now here's what REALLY confuses me. The coarse internal threads of the end-cap must screw onto the shaft threads at the same time it is screwing into the fine internal threads of the bare UCA. I don't understand how this can be done. Then ...when both end caps are screwed into the UCA as far as they will go, and the shaft is captive between them, the shaft will be locked in a bind unless you loosen one or both end-caps slightly so the shaft can rotate in the coarse internal threads with the least amount of twisting force.
The way I understand the assembly, after it's COMPLETELY assembled, you can rotate the shaft about 3 or 4 total full turns from CW to CCW with your bare hand (or a little more).
Now here's what REALLY REALLY REALLY confuses me. Three or four turns from stop-to-stop means that the entire UCA moves forward and aft, on the car, as the suspension does its job on the road. From memory, the coarse threads are about 0.100" per revolution. I estimate full suspension travel of the UCA to be 15 degrees.
That would mean that the fore/aft movement of the UCA would slightly change the caster as you drive and the suspension does its job. Not much, but it does change.
I STILL don't totally see how to assemble it though. Any insight??
