Older trucks were 'gear bound' while todays trucks focus on reducing rolling resistance.
Old R model Macks with the Maxitorque 5 speed [signs said hill ahead; Macks downshift NOW!] and with only 5 gears the torque was hard to control in 1st gear when rolling over uneven surfaces.
Part throttle caused surging as the bumps were transmitted to the throttle. The only smooth way was foot off the pedal -or- mashed down against the stop