Huh? 20K miles?? You're gonna have guys drooling all over their keyboards when they see that!

Anyway, if I recall the parking lock mechanism is a "pawl" that engages notches in the flywheel. Not really a transmission thing. Quite possibly a transmission shift linkage problem. Or maybe the pawl got broken off, but I think that's not so likely.

Your shift lever works a long bar linked to a lever on the tranny. The link bar connection is adjustable.

Also - and this is quite possible due to age - the motor and transmission mounts can fail. When they do, the engine/tranny assembly shifts position. Since your shift lever stays where it is, it is now out of adjustment. Cure for that is to replace the failed mounts. One at each side of engine, one under rear of tranny where it rests on the cross member. Right side engine mount is under the oil filter; if you slide a finger under the filter you can feel the mount. Should be nearly enough room to fit a finger between filter can and mount. If no gap, mount is definitely bust-o. Can be viewed from below.
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Sven: '89 245 NA, 951 ECU, expanded air dam to 7' from ground, forward belly pan reaches oem belly pan, open-front airbox, E-fan, 205/65-15's at 44 psi, IPD sways, E-Codes, amber front corner reflectors, quad horns, tach, small clock. Wifemobile '89 245