You did not really answer my question. What do you mean by dragging/seizing? Seizing to me means they are stuck and will not move. Is it 1 or both sides? The piston can stick in the caliper. Just had one of those the other day. Not likely both sides would do it at the same time but it is possible.
Take the wheels off, start the engine and apply the brakes. Turn off the engine and go to a wheel where the rotor will not turn. Open the bleed screw. If you get a little squirt of fluid under pressure something is not letting fluid return to the master cylinder and with the bleed screw open the rotor should turn or turn easier. A hose can cause this but you have replaced them so it must be something else. If no fluid comes out under pressure it is probably the piston sticking in the caliper.

When you changed the booster are you sure the push rod is adjusted properly (the correct length for the master cylinder). If the push rod is going into the master cylinder too far the master cylinder piston cannot return all the way. This might be keeping the fluid pressure from returning to the mastercylinder when you let off the brake.

 

its both sides dragging. doth sides are very hot when i drive a mile or so. I'm going to change the calipers again because i think that it is the bad brake fluid in the system(its very dark like oil).

 

Try the ideas above before changing calipers.

Moisture collecting in the fluid over time can cause corrosion which can lead to sticking calipers. So yes flush with new fluid. Some manufacturers call for changing brake fluid every 3 years.

 

I've been fighting a similar problem on a 2001 4WD for a couple years now and looking for ideas. About twice a year, I need to pull the front calipers off because they bind/stick on the slide pins. Unlike older models, mine are inside the brake mounting bracket. Usually when I remove the pins, the rubber insert comes out also. I clean up the old grease/lube, wipe the pins down (they are nice and shiny-no rust), re-lube everything, push the inserts back in and the caliper moves freely. Six months later, I have to do it again. Already replaced the pins and rubber inserts once. I've tried several kinds of lube, nothing seems to make a difference. If this was a big problem, I would have thought someone would come up with a bronze bushing for the insert.
Thoughts/suggestions welcome.

 

If you continually have to re-grease the pins to keep them freed up, you may want to look at replacing the caliper bracket. The bores the pins ride in may be worn out causing them to bind up. The brackets can be purchased for ~$10 each and I would put in new seals & pins as well. Use a good synthetic caliper grease on the new pins and see how that goes.

 

Sorry, I had this a little backwards. The pins screw into the caliper, but the remainder of the pins go into holes in the mounting bracket itself. There is a rubber accordian seal between the bracket and caliper and the end of the pins go into a rubber 'bushing' that is in the bracket. There is no metal-to-metal contact between the bracket and pin. From what I can tell, these rubber bushings are what the caliper/pin slides on.
The seals are all good-there isn't dirt or water getting in. The rubber bushing just seems to bind to the pin after a while. I've tried wheel-bearing grease, brake grease, lithium grease, and graphite. None seem to last longer than 6 months.

 

I am well aware of how they go together. You have a problem and you have replaced everything else. It's something to try. While you are at it, get a good quality synthetic caliper grease.

 

Did you ever figure out the problem? My truck is doing the same thing.

 

This is on a 2001 (or similar year) model, right? I haven't had the time/motivation to pull everything apart yet, but it needs to be soon. I've been trying to get my head around the design. The thin end of the caliper pins rests in a rubber bushing that is inside the mounting bracket. It seems that over time, this rubber bushing swells and binds the pin. I replaced them a couple years ago-still trying to understand why rubber ones were used. Next time I pull the front brakes apart, I'll either replace the bushings again, or maybe look at putting bronze sleeves in.
Once I do it, I'll update this thread.

 

I had one that would lock up like that and it was the flexible hoses.
stepping on the brake hard would lock them and they would slowly let go over about 5 minutes. couldn't drive it until i fixed it.