I have a problem with my truck. 2004 Silverado 2500HD 6.0 vortec and 4L80E with 138k miles that happened for the first time last week. I drove it normally one day. Parked it on flat ground and then came back the next day. Starts and runs fine. I press in the brake to shift out of park and it won't budge. I even put some muscle behind it and if I put anymore something will definitely break. I did some research some people say it's the brake light switch. So I replaced that and still nothing. Brake lights work fine. I can't get it out of park with the key in any position. I have rocked it back and forth to loosen the pressure on the tranny and it still won't budge. I'm stumped. I've heard it could be anything from the brake/transmission solenoid to the interlock shift. To the ignition switch.. I don't know. I've done little research and have very little time to work work on due to my job. Any help would be appreciated.