Is it brakes or tranny?
I guess before spending a bunch of money on new expensive parts, I'd have the calipers removed and brakes completely inspected. There could be corrosion on the pins, a rotor could have a large ridge, or there might be corrosion on the ends of the steel backing plate (of the pads) themselves. Or corrosion under the stainless 'sleeves' which are on each side of the brake pad backing plate. One common thing which can occur is corrosion builds up under the stainless sleeve and *pinches* (squeezes) the pad tight. When the caliper pushes it in during a stop, the pad can't freely back off like it normally would
. Sometimes a pad can get stuck and if ya put the vehicle in R for a second and back up a little, then forward the pad can 'pop' free (move back from the rotor). Pad seizing is a fairly common thing in our area where road salt is used. They can get so tightly lodge in there it takes a hammer to remove them! Another thing that can happen is, a mechanic DOESN'T reinstall the stainless sleeves, and a ridge (groove) develops where the steel pad tab rides. And pads can get caught in the groove and lodge against the rotor. Seen that a bunch of times too.
The caliper guide pins and all the caliper/pad sliding surfaces need to be carefully checked and cleaned of corrosion ...and lubed too. These are easy to check and you have to rule out the common, simple things first. But of course, it all takes time and mechanics don't typically like to take the time to do work that won't involve pricy new parts, so it's somewhat counter-productive to how they get paid. But the point is, the brake pads and calipers need to slide in/out freely so no brake binding occurs.
Eliminate that possibility first.
Then a good brake bleed (exchange fluid for new) would be in order. Shops have a machine which makes this job super-easy. I would do that to ensure there isn't water in your brake system freezing (causing binding) when it's cold (and liquifying when warmed up).
Then after that look at all the electrical connectors to the ABS...things like that. It could be an ABS valve body, but eliminate the larger possibilities first.
Anyway, your truck is ~8yrs old, so these things listed above are maintenance tasks which should be looked at and fluid exchanged anyway. Part of good maintenance and helping reduce unnecessary long-term failures or expensive repairs. So, it's not a waste of money to do a comprehensive brake inspection/service, even if the problem ultimately ends up being something else. I remove my vehicle calipers and clean/repair at least once a year ...when I have the wheels off (like, say, for rotating). It keeps overall costs down.
Best of luck. Let us know what it ultimately turns out to be.
[Note: for the sake of clarity, I rotate tires more than once a yr ]