TM 9-2350-256-34-2
Table 2-3. Troubleshooting-Continued
MALFUNCTION
TEST OR INSPECTIOS
CORRECTIVE ACTION
MECHANICAL TRANSMISSION AND MAIN HYDRAULIC PUMP CIRCUIT
(MAIN HYDRAULIC SYSTEM)-continud
engine operating at 1800 rpm, and power control valve lever in ON position, normal operating pressure should
be l50 ± 10 psi.
a Remove mechanical transmission and main hydraulic pump assembly. Refer to TM 9-2350-256-34-1, Medium
Recovery Vehicle, M88A1.
b. Replace mechanical transmission Refer to paragraph 3-16.
19. MECHANICAL TRANSMISSION FAILS TO DISENGAGE MAIN HYDRAULIC PUMP
Step 1. Test for hydraulic overload. Remove hose no. 66 from mechanical transmission clutch housing. If mechanical
transmission disengages with hose removed, it indicates a faulty power control valve.
Replace power control valve. Refer to TM 9-2350-256-34-1, Medium Recovery Vehicle, M88A1.
Step 2. If mechanical transmission does not disengage with hose removed, it indicates a faulty mechanical transmis-
don clutch assembly.
a Remove mechanical transmission and main hydraulic pump assembly. Refer to TM 9-2350-256-34-1, Medium
Recovery Vehicle, M88A1.
b. Replace mechanical transmission. Refer to paragraph 3-16.
20. MAIN HYDRAULIC PUMP NOISY
Step L Inspect hydraulic reservoir for low oil level.
Add oil to bring to proper level. Refer to TM 9-2350-256-20. Medium Recovery Vehicle, M88A1.
Step 2 Inspect for collapsed main hydraulic pump suction hose.
Replace suction hose. Refer to TM 9-2350-256-20, Medium Recovery Vehicle, M88A1.
WARNING
Test components must be capable of withstanding a working pressure of 1950-2050 psi (Step 3 only)
NOTE
After performing main hydraulic pump test, return all plumbing to original configuration.
Step 3. Test main hydraulic pump. Remove check valve and tee between hose no. 4A and 4B. Install main hydraulic
pump pressure tester kit (Item 14, Table 2-1) between hose no. 4A and hose no. 4B. Install test pressure gage in
tee.
CAUTION
Make sure that the load valve is in full open position before performing test. When performing main
hydraulic pump pressure test, do not restrict oil flow beyond opertaing pressure.
With main engine operating at 1800 rpm operating pressure should be 1950-2050 psi when restricting flow
using load valve.
After testing remove hose no 4B from pump port no. 1. Remove pilot-operated relief and unloading valve
assembly from pump port no. 44. Install hose no. 4B on pump port no. 44.
With main, engine operating at 1800 rpm. operating pressure should be 1950-2050 psi when restricting flow
using load valve.
a.
Remove mechanical transmission and main hydraulic pump assembly. Refer to TM 9-2350-256-34-1. Medium
Recovery Vehicle, M88A1.
5. Replace main hydraulic pump. Refer to paragraph 3-16.
2-14
Change 7
