Section VI. HYDRAULIC PUMP

TM 10-3930-630-34

Section VI. HYDRAULIC PUMP

inch (44.5 mm), the gear must be replaced. Replace

3-22.

Description

gear assemblies if journal surfaces are blackened.

a. The hydraulic pump supplies hydraulic oil

Shafts and gears must be replaced as assemblies.

under pressure to operate the hydraulic components.

Inspect bushings for scratches or cuts.

The gear type pump is directly driven by the engine

Minor scratches can be removed by honing in a circular

crankshaft.

motion with a fine stone. Check to be certain sharp edge

b. Oil is drawn from the reservoir through a

between face of bushing and the outside diameter is not

suction line. The oil is then delivered to the

broken.

control valve and steering gear valve for

The bore of the bushing, which will be worn

distribution to the cylinders.

slightly oval, must not measure over 0.881 inch (22.3-

3-23.

Hydraulic Pump, Removal and Disassembly

mm) at the largest reading. The length of the bushing

a. Removal. Refer to paragraph 2-12 and

must not measure under 1.055 inch (26.7-mm). If these

remove the hydraulic pump.

tolerances are not met the bushings must be replaced.

b. Disassembly. Disassemble the hydraulic

k. Wash spool valve and dry with

pump in numerical sequence as illustrated in figure 3-9.

compressed air. Valve must slide freely in and out of its

NOTE

bore. Check diameter of all lands and replace spool if

any are less than 0.748 inch (18.9 mm). Clean orifices

If bushings (9 and 13) stick, tap body

with a fine wire.

on a piece of wood to prevent

Check valve spool spring for bends, cracks

marring mating surfaces. Care must

or deformation. Replace spring if free length is less than

be taken not to damage surface of

3.5 inch (88.9 mm).

the bushings.

m. Inspect the relief valve plunger for wear

3-24.

Hydraulic Pump, Cleaning, Inspection and

and erosion. Replace if damaged.

n. Inspect relief valve spring for bends,

Repair

cracks or deformation. If free length is less than 0.80

a. Clean all metal parts in cleaning compound

inch (20.3 mm), replace spring.

solvent (Fed. Spec. P-D-680). Dry thoroughly with

compressed air.

b. Using a 2-inch (50.8 mm) inside

3-25. Hydraulic

Pump,

Reassembly

and

micrometer check the bushing bores near the front of

Installation

the housing. If bores measure over 1.770 inch (44.9

a. Reassembly.

mm), discard the pump body.

(1) Before reassembling the pump check to be

NOTE

certain all parts are clean and dry.

This is an indication that pump has

(2) Place pump body (30, fig. 3-9) face up and

install body dowels (29). Tap in place with a plastic

been

subjected

excessive

hammer. Coat body bores with light oil (OE/HDO).

pressure and the system must be

(3) Place new packings (15) and wear rings

checked to determine the cause.

(16) on the shoulder of rear bushings (13). Hold in place

c. Inspect parts for nicks and burs. Remove

with grease if necessary. Coat faces and bores of the

with emery cloth if possible. If damage is severe,

bushing with light oil. Be sure bushings (13) bottom in

replace parts.

body (30) and wear rings do not fall off. Place dowel

d. Inspect inside of bores for burs and remove

(14) in bushing holes and holding bushings (13)

with emery cloth.

together, carefully align them and slide them into the

e. Place a straightedge across the machined

bores.

mating surface of the flange. If the flange is bowed,

NOTE

replace flange.

Do not force bushings into bores.

NOTE

They must slide to the bottom of the

Bowing of flange is caused by

bore with hand pressure.

excessive pressures and the cause

(4) Coat gear shafts and gear faces lightly with

must be determined before installing

oil (OE/HDO). Turn pump body so that bore for spool

the pump.

(28) is to the left and place drive gear (11) in top bore

Hone flange mating surface to remove

and idler gear (12) in lower bore.

burs, scratches or other damage. Clean thoroughly.

(5) Position front bushing dowel pin (10)

g. Inspect drive gear and idler gear for

between bushings (9), hold bushings together and

damaged or worn splines or gear teeth. Remove burs

with a fine hone.

h. If length of gear is less than 1.320 inch

(33.5 mm) or if gear outside diameter is less than 1.754

3-14