2nd Gen Non-Engine/Transmission Rear brake smoked

[VolsFan]

Hi, today my right rear brake smoked pretty bad under normal driving. I put new rotors and pads all the way around few months ago, and now have new calipers and hoses up front, only thing that is not new is the rear calipers. Drivers side is ok. I put the new calipers/hoses on the front because of a smoking issue, problem solved. I bled the front til fluid was clear, didn't bother doing the back. Just now bled the rears, hopefully will fix the problem? Only other thing will be new calipers and hoses for the rear I guess

 

[VolsFan]

Ok, got new calipers and seems to have fixed the problem , old ones were pretty bad. Question I have- before I pushed the brake pedal in pushing out the piston in the caliper, the drive shaft was turning and spinning the hubs. Not fast but spinning them none the less and truck was not in gear. Once I had the brakes set to where they should be it stopped. Why would the driveshaft be spinning even when the transmission is in neutral?