Like the SD40-2 the GP40-2 has a reputation for reliability, and many are still in use.
With the usual 62:15 gearing (65-70 mph maximum) EMD rated the GP40-2 at 55,400 lb continuous tractive effort; for compatibility with other units, most (all?) had the PF21 module that reduced horsepower below 23 mph, bringing the minimum continuous speed down to 11 mph.