Something I’ve been wondering about....
What was the idea with the threaded shackle pins on these early trucks? Thinking specifically about the rear suspension, rear shackles on an AD truc.
If I picture in my mind how this works: spring compresses, shackle pin has to rotate, rotation along the threaded pin causes it to move to one side or the other. And that happens non stop, all the time, as the vehicle is driven.
Would seem that the “seal” would be constantly compressing on one side and opening up on the other.
That's the way they would work. The seals on the replacement shackles I bought are rubber washers, where the originals were felt, so the newer ones should compress and relax better.
The shackles only rotate a few degrees, so the lateral movement is pretty limited. The shackle threads are 5/8 x 11 TPI and would only move 0.09 inches per full revolution. So for say a 10 degree rotation of the shackle, that would only be only about 2-1/2 thousandths movement.
