06 feb 2022
More than you ever wanted to know about early Rambler American pitman arms. More than I ever wanted to pay attention to them, but there are two systems, and they are not interchangeable. I found out only when I installed the wrong one by juggling parts from the pile without paying sufficient attention.
There are what I'm calling early and late systems. Late is definitely 1961 to 1963. Early may go back before 1958 but I have no data, but it is certainly a Nash-designed part. There is a corresponding early vs late steering box and pitman arm. The net effect is the location of the tubular steering link, fore/aft. The early system pushes it closer to the front of the car about and inch, and later, it runs closer to the engine.
The steering linkage wants to be exactly perpendicular to the direction of travel. The car will "work" with wrong parts, but steering geometry (toe, and Ackermann angle) will be wrong in turns. Given these are not generally used as sports cars (though they do that far better than you'd ever imagine) you might not even notice... but the car might feel funny and tire wear will increase unevenly.
Mainly though for folks who don't do the foolishness I do, you need to know the difference regarding idler arm bushings or replacement arms with bushings installed.
|58..60? "Early"||MEVOTECH MS404121||1.14 OD/.63 ID x2.31". 50's Ford, and some later AMC (79 Spirit). This part has no flange on the outer sleeve.||.953" (61/64") from 1958 TSM|
|61..63? "Late"||K3026||1.14OD/0.72 ID x 2.44". This part has a flange on the outer sleeve.||.6875" (11/16") from 1963 TSM|
The bushing needs to be pressed in to a fairly precise distance from the pivot.
For far more technical information and family history compiled by the Australian Rambler Club, refer to the idler/pitman arm document in my Documents section.
Note that in a pinch you could install the K3026 part in the early arm; the press-fit part size is identical, the overall length within the range of the nut and threads, but you would need to shim the pivot with thin sheet metal. Beer can metal would work; the steering geometry error would be immeasurably small, the innert sleeve is fixed and does not move, the arm pivots by the outer sleeve rotating around the inner with the intervening rubber as "bearing".