If the truck is the 4WD version, it has the A340F transmission.
Since the noise is heard in N and P, it can likely be narrowed down to the torque converter, oil pump, O/D input shaft bushings and bearings or the O/D planetary carrier. These are the only items that spin when the transmission is in N or P. These are all in the front of the transmission and easily accessible once the transmission is removed.
Transmission shops don't like to do spot repairs on high mileage transmissions. If they fix a noise problem and nothing else, they would likely be blamed if a totally unrelated transmission problem happens a couple thousand miles later.
Since the noise is heard in N and P, it can likely be narrowed down to the torque converter, oil pump, O/D input shaft bushings and bearings or the O/D planetary carrier. These are the only items that spin when the transmission is in N or P. These are all in the front of the transmission and easily accessible once the transmission is removed.
Transmission shops don't like to do spot repairs on high mileage transmissions. If they fix a noise problem and nothing else, they would likely be blamed if a totally unrelated transmission problem happens a couple thousand miles later.