Take the soft line off the caliper (remove the banjo bolt), and see if you can easily move the piston back. If it is, you have a line issue. If not, the piston is hung in the caliper. My $ is on the soft line...

 

This one is my favorite, since we're talking squeezing calipers... really fast and effortless

 

Ooo, that's kinda cool. Where did you get that?

 

I used this one before and love it

 

Just found these. I'm not sure if it's the same brand though.

 

Thank You.

 

I had the same issue. I pulled my guide pins and the old grease felt like the wax used in a wax ring on a toilet. They've been cleaned and greased and now move easily.
The issue now is that I've been driving my car with four wheel disc brakes and weighs half as much as the truck for a while and the trucks brakes feel like I'm using Flintstone brakes on a semi compared to it.

 

1. Nice name lol 2. I did just that and they seem to be working well today, just needed more grease I think. And, while I was in there I tried to press the brake pads in a little bit and I could move it a tad with just my hands so I think that's fine for now, not really sticking as much as it used to. I plan on moving next month, so I'll probably change out the pads one more time just to get them all at 100%, so I'll update you guys if that was the only issue when I get more braking time in lol.

 

Yep that is the tool... I don't think I paid that much, had them for a while.