TM10-3930-660-20 18-8. PRIORITY VALVE - REPLACE This task covers: a. Removal b.  Installation Initial  Setup Tools Tool Kit, Automotive Mechanics Materials/Parts Container, 1 Gal. Lockwashers  (6) Cap and Plug Set Loctite 242 (App. C, Item 39) Tags (App. C, Item 51) Equipment  Condition Vehicle parked on level ground. Parking brake set, wheels chocked. Hydraulic oil in the system can be under pressures over 3000 psi with the engine OFF . ALWAYS relieve pressure in hydraulic lines before attempting to remove any component in the hydraulic system. With engine OFF, starter switch in RUN position, and MLRS attachment on the ground, move control levers through all operating positions several times to relieve line pressure. Relieve pressure in hydraulic oil tank by loosening filler cap very slowly. Failure to follow these precautions could result in serious personal injury. At operating temperatures, hydraulic oil is hot and under pressure. Hot oil can cause  injuries. Allow hydraulic oil to cool before disconnecting any hydraulic lines. The priority valve is located under the vehicle toward the rear of the cab mounting  shelf. 18-34