My 1992 chevy silverado is stuck in park.there wasn't much warning.trans was shifting fine.had been a little hard to get out of park a few times,especially parked ona slope.I rocked the truck back and forth,checked linkage,even picked rear wheels off ground.any ideas?

Check and, if necessary, adjust/replace the ATX shift lock solenoid. The shift lock system prevents the shift lever from moving to Reverse from the Park position, unless the brake pedal is depressed and the accelerator is in its rest position.