Dually w/ 70HD diff, temp warm at pinion question

[JellyBeanDriver]

Working on the ranch truck today - inspecting rear brakes.

Drove it from cold 8 miles from the ranch to my house. Crawled under the truck and inspected the drivetrain, feeling the u-joints, diff, etc and surprisingly found the diff was warm on the pinion shaft end. Axle at the wheels was stone cold. Rear cover was a little warmer but not much. Diff at pinion end was definitely the warmest part.

Surprised that only 8 miles would do this.

Normal? Can pinion preload account for this or is there something more sinister going on?

Thanks