What was found
GEAR WOULD NOT RETRACT AFTER TAKEOFF. HYDRAULIC PRESSURE WAS 0 PSI. HYDRAULIC QUANTITY WAS NORMAL. ACCOMPLISHED LOSS OF HYDRAULICS CHECKLIST. SYSTEM OPERATED NORMALLY ON AUX PUMP. FOUND AIRCRAFT WAS BELOW STANDPIPE LEVEL. SUSPECT AIRCRAFT HYDRAULIC QUANTITY WAS SERVICED INCORRECTLY AFTER HYDRAULIC TEST STAND REMOVED. NO LEAKS NOTED ON AIRCRAFT. REPLACED BOTH ENGINE DRIVEN HYDRAULIC PUMPS IAW DC-8 AMM 29-10-12-2 AND BOTH CASE DRAIN FILTERS IAW 29-10-15-2, DUE TO LACK OF HYDRAULIC FLUID. LEAK CHECKED GOOD. SERVICED HYDRAULIC QUANTITY IAW DC-8 AMM.