CHAPTER 6 REPAIR OF MAIN HYDRAULIC SYSTEM

TM 10-3930-634-34

CHAPTER 6

REPAIR OF MAIN HYDRAULIC SYSTEM

Section I. HYDRAULIC VALVES, HYDRAULIC CYLINDERS, HYDRAULIC

RESERVOIR AND HYDRAULIC MANIFOLD

6-1. General

pump. The correct pressure is 2000-2100 psi. Adjust

the pressure setting at the valve as necessary to obtain

This section contains information on the maintenance

the correct reading at the hydraulic pump.

of the hydraulic valves, hydraulic cylinders, hydraulic

reservoir and hydraulic manifold that is the responsi-

6-3. Two-Spool Valve

bility of direct support and general support mainte-

nance personnel.

a. General. The two-spool valve controls the side

WARNING

shift and oscillating operations.

Relieve oil pressure by operating controls

b. Removal.

with engine OFF before opening lines or con-

(1) Tag all lines for identification before removal

nections.

to assure proper reassembly.

NOTE

(2) Remove the console panel at the right of the

Tag all hydraulic lines before removing them.

driver's seat to gain access to the valve.

After removal, cap or plug all openings to

(3) Refer to figure 6-3 and remove the two-spool

valve.

prevent the entrance of dirt.

c. Disassembly. Refer to figure 6-4 and disassemble

the two-spool valve.

6-2. Three-Spool Valve

d. Cleaning and Inspection.

a. General. The three-spool valve controls the lift,

(1) Clean all parts carefully, using solvent

tilt, and extension operations.

P-D-680 or equal.

b. Removal.

(2) Inspect the plunger (6, fig. 6-4) and the pilot

(1) Tag all lines for identification before removal

seat (7) for nicks, burrs and scratches.

to assure proper reassembly.

(3) Inspect the spool (32) for scratches and other

(2) Remove the console panel at the right of the

damage.

driver's seat to gain access to the valve.

(4) Inspect all other parts for distortion,

(3) Refer to figure 6-1 and remove the three-spool

scratches, burrs and other damage.

valve.

(5) Inspect all tubing and linkage for breaks and

c. Disassembly. Refer to figure 6-2 and disassemble

bends.

the three-spool valve.

(6) Replace all defective parts.

d. Cleaning and Inspection.

e. Reassembly. Refer to figure 6-4 and reassemble

(1) Clean all parts thoroughly using solvent

the two-spool valve.

P-D-680 or equal.

f. Installation. Refer to figure 6-3 and install the

(2) Inspect the pilot plunger (20, fig. 6-2) and the

two-spool valve.

pilot seat (21) for nicks, burrs, and scratches.

g. Adjustment. Check the pressure at the hydraulic

(3) Inspect the spool (32) for scratches and other

pump. Correct pressure is 2100 psi, + or 25. Adjust

damage.

the pressure setting at the valve as necessary to obtain

(4) Inspect all other parts for distortion,

the correct reading.

scratches, burrs, and other damage.

CAUTION

(5) Inspect all tubing and linkage for breaks and

Do not adjust pressure too high or damage

bends.

will occur to brake applicator valve.

(6) Replace all defective parts.

e. Reassembly. Refer to figure 6-2 and reassemble

6-4. Dual Overcenter Relief and Replen-

the three-spool valve.

ishing Valve

f. lnstallation. Refer to figure 6-1 and install the

a. Removal.

three-spool valve.

(1) Remove the console panel at the right of the

g. Pressure Check. Check pressure at the hydraulic

6-1