Same pulsing, thought for sure it was the front, and was getting ready to install new pads.
Just recently, I found that my parking brake was not releasing fully, so asked the dealer to adjust it during a check up... sure enough, my rear drum was burnt and had to be replaced, (warranty), sure enough, no more pulsing.
I didn't feel the parking brake bind while driving, and it would roll in neutral, but I couldn't push the truck while in neutral easily. I could see it going unnoticed if you have an automatic.