490 - EXCAVATOR 21 MAIN HYDRAULIC SYSTEM 21 Parts group 21 MAIN HYDRAULIC SYSTEM 21 HYDRAULIC SYSTEM 2160 . HYDRAULIC RESERVOIR [01J19] HYDRAULIC FILTER RESTRICTION INDICATOR [01J21] DIFFERENTIAL SWITCH [01J23] Select group 21 MAIN HYDRAULIC SYSTEM 21 John Deere: HYDRAULIC SYSTEM 2160