1989 GMC Pick-up Truck Differential Rebuild Kit K3500 - 4WD - GM 9.25 in. IFS - Clamshell Differential - Master Overhaul Kit - Timken Bearings - Front guaranteed to replace your current 1989 GMC Pick-up Truck Differential Rebuild Kit K3500 - 4WD - GM 9.25 in. IFS - Clamshell Differential - Master Overhaul Kit - Timken Bearings - Front. 1989 GMC Pick-up Truck Differential Rebuild Kit comes new OEM 1989 GMC Pick-up Truck Differential Rebuild Kit aftermarket new 1989 GMC Pick-up Truck Differential Rebuild Kit of remanufactured 1989 GMC Pick-up Truck Differential Rebuild Kit K3500 - 4WD - GM 9.25 in. IFS - Clamshell Differential - Master Overhaul Kit - Timken Bearings - Front.