TM 10-3930-659-20 17-4. HYDRAULIC CYLINDER DRIFT/LEAKAGE TESTS (Con't). 6. Start engine (see TM 10-3930-659-10). 7. Raise carriage assembly (5) 3 ft (1 m) above ground and place two trestles under fork/boom assembly (6). 8. Shut down engine (see TM 10-3930-659-10). 9. Measure distance between one fork (4) and ground.  Wait one minute and repeat measurement.  Record change in distance. 10. Wait 10 minutes and repeat measurement in step 9.  Wait one minute and take measurement again.  Record change in distance. 11. Compare changes in measurements in steps 9 and 10.  If drift is same for each of the two one minute periods, replace forklift control valve (see paragraph 17-8).  If drift is less for second one minute period, replace carriage tilt cylinder (3) (see paragraph 17-9). 12. Remove two trestles from under fork/boom assembly (6). b. FORK/BOOM CYLINDER DRIFT/LEAKAGE TEST 1. Start engine (see TM 10-3930-659-10). 2. Park forklift truck on a firm surface and raise carriage assembly (5) 3 ft (1 m) above ground. 3. Shut down engine (see TM 10-3930-659-10). 4. Attach masking tape (8) to rod (7) exactly 2 in.  (5 cm) in front of fork/boom cylinder (9). 5. Wait one minute and measure distance between masking tape (8) and fork/boom cylinder (9).  Distance change must be less than 0.12 in.  (3 mm).  If measurement is within specification, check is complete and tape can be removed.  If measurement is not within specification, continue with test. TA707619 17-14