When the key in my 1984 started getting hard to turn I took it apart before my kid broke the key off to make bigger problems. The problem wasn't in the tumblers, which are the first suspect. I pried off the steel cover at the rear side and found there is a spring detent in there. The spring holder is thin die-cast metal which had broken off, leaving the pieces to rattle around inside and sometimes jam the turning. I just left those parts out and pinned & epoxied the cover back. The key rotates easy now but never rotates out of position while driving. I probably should have just removed the steering lock rod while "in there" since I doubt it prevents theft, is a risk of locking the steering wheel while driving. But, most importantly, the steering lock can load the key cylinder when parked so that a dumb kid might try to force the key and break it off (teenagers and/or spouses). Not all know to turn the steering wheel slightly to unload the lock so the key turns easy, or will listen. If you wonder why I didn't trust my kid, he once ripped the net off the back driver's seat when removing a bicycle from the rear seats, a pedal snagged on the net, which frustrated him so just pulled harder. Why he didn't put the bike in the trunk I don't know. He was a medical student then and now a rich M.D so can move on to vandalizing a new high-end M-B or Tesla.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans