If that's your truck in your sig Dan96Xj, mud might be your problem. It certainly was on my TJ. My piston locked tight and I kissed my rotors good-bye. Needless to say it scared the bajeebers out of me and could have been a very messy situation.
I tend (well, try anyway
) to stay out of the mud these days, but I rebuild my calipers every couple years now. It's probably overkill, but it's cheap (~ $50 per side for a rebuild kit) and easy to do.
I think it's worth it to know that the brakes will be there when you need 'em!