1981 GMC Pick-up Truck Differential Carrier K3500 - 4WD - Dana 60 - Yukon Grizzly Locker - 30 Spline - 4.10 and Down or Thick Gear Ratio's - Front guaranteed to replace your current 1981 GMC Pick-up Truck Differential Carrier K3500 - 4WD - Dana 60 - Yukon Grizzly Locker - 30 Spline - 4.10 and Down or Thick Gear Ratio's - Front. 1981 GMC Pick-up Truck Differential Carrier comes new OEM 1981 GMC Pick-up Truck Differential Carrier aftermarket new 1981 GMC Pick-up Truck Differential Carrier of remanufactured 1981 GMC Pick-up Truck Differential Carrier K3500 - 4WD - Dana 60 - Yukon Grizzly Locker - 30 Spline - 4.10 and Down or Thick Gear Ratio's - Front.