That coupling looks very suspicious. The metal parts appear to show evidence that they have been contacting each other, which shouldn't be happening. They're only there as a "fail safe" in case the flex coupling fails. That's probably one of the reasons the steering is squirrely. Also check the cab to frame mounts. One reason for repeated rag joint failures is sagged or rusty front cab mounts which puts stress on the rag joint from misalignment of the shafts.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!