Welcome to the Forum from NH.
Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.
I hope that you will become a participating member in the Forum's discussions.
Pics of the truck, please. If we can't see it, it does not exist.
My guess is that it is brake related. I would fully check out the disc brake caliper and pads to see it something is amiss there. If that looks good, I'd dig further into the assembly and check out the emergency brake shoes and hardware.
Other members of this Forum much more knowledgeable than me in this area will chime in.