I have the same problem on my '89 w/ AT... and the good ol' paper Toyota FSM dosn't have any info on it either.
I'd love to have a solution though. I tried taking it apart once - best I could tell, there are bushings at the base of thr shiufter that are shot (wallowed out). But I couldn't figure out how to get them out w/o dropping the whole unit. Grrrr.

With 200+ Billion electrical parts, the world most complicated machine is inside your own skull.

Question Reality.
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'89 Rnr DLX "SR4.5", 32s w/ 5.29 locked f/r blah blah