Coincidentally, I have been working on the column from my ‘71 Duster. I had rebuilt it (for the third time) but when finished it was making a scraping noise up top when turning. The shaft was collapsed and the lock collar was worn out and wouldn’t stay locked so I decided to replace the shaft with another one I had.
I did try to separate the two halves of that one first to see if I could re-pin it but gave up because the plastic wouldn’t allow it. I tried hammering the outer lip of the lower half with a 5/8” crow foot socket on an extension, I tried melting the plastic with a torch and all sorts of other dumb stuff but it would not come apart. It was pitted at the bottom anyway so it’s junk.
The other shaft I had was also collapsed but I was able to separate the two halves on that one fairly easily. See the pics below.
IMO the shear “pins” are not actual pins but merely excess material that stays in the injection holes after the troughs are filled. It’s easy to see how they would break without much effort because they are more like drops than a machined pin. I have no doubt that over time the plastic dried out, shrank, became brittle and then it was only a matter of time until the pieces separated.
This is the bottom of the upper half that gets inserted into the female end if the lower half. There are no “through” holes in these recesses so again, there really are no pins in the traditional sense. You can see the remnants of the plastic, it’s similar to nylon.
Lower half Injection holes.
I’m not sure what year the shaft I separated was but has to be ‘70-down because there is no lock plate pin bore. it’s otherwise identical to a ‘71.
I would actually like to know what length a ‘71 manual steering shaft is supposed be so I can try and use this good one. I’ve read 40 5/8” end to end but I can’t find anything “official”.