Need increased pressure to release shifter

On my 90 4.0 auto I have to, recently, use increased brake pedal pressure to get it to release out of park. Is there a switch or something going bad or an electrical issue going on here?

Does it only happed when your on an incline?

No I'm on flat ground. Thats all we have here in my neck of the woods. I have noticed its worse when it is cold.

Check the stoplight switch. Power from it should release the shift lock solenoid when you step on the brake. Also check the wires to the stoplight switch. Sometimes the wire breaks inside the insulation from flexing. IIRC if you turn the key to "unlock" (but not "on") you should be able to shift without stepping on the brake.

One more IIRC, the shift locks were added as a recall and may have a lifetime warranty. If a part of it is faulty you might call the Dealer ask.