I had my shifter button start to stick over 3 days, finally jamming completely in Park at work, and I tried everything I could to push it in. I tried pliers (wrapped in cloth), I tried hitting it with my fist (painful), I tried pressing a metal rod on it to get leverage. Nothing. Wouldn't budge. Just as I was about to try a tow, I got on the forums and saw it was a lubrication problem. I tried to remove the shifter knob as suggested in a couple of threads here, but no luck. Mine wouldn't turn, even with a wrench (wrapped in cloth). I decided on one last desperate measure - WD-40. I got the straw and sprayed it in the crack between button and shifter knob in a couple of spots. Worked like magic. Instant un-stuck!
I then took the car into the dealers anyway and had the shifter knob replaced just to be safe, since I doubt WD-40 is an approved lubricant, but now I know I won't get stuck again.
I then took the car into the dealers anyway and had the shifter knob replaced just to be safe, since I doubt WD-40 is an approved lubricant, but now I know I won't get stuck again.