Idler Gear Assembly

TM 10-3930-242-34

gear hub are scored and worn excessively, they

h. I n s t a l l a t i o n .

m u s t be replaced.

( 1 ) Lubricate bearings and shafts with en-

g i n e oil and slide the shaft assemblies into the

NOTE

c y l i n d e r block being careful not to damage the

When a new bearing is being installed in the idler

b e a r i n g s or the cams and journals. Make sure

gear, it must not protrude beyond the gear face on

either side.

t h a t the appropriate timing marks on the gears

are aligned. "Gear Train and Engine Timing" is

(2) Slide the idler gear straight back off of

c o v e r e d in paragraph 333.

t h e idler gear hub.

( 2 ) Slide an oil slinger on the front end of

( 3 ) Remove bolt which secures the idler

both shafts.

gear hub to the cylinder block. Then, remove the

(3) Install the upper engine front cover

idler gear hub and the rear idler gear thrust

(para 3-28).

w a s h e r , as an assembly, from the engine.

( 4 ) Secure the thrust washers in place and

d. Installation.

t i g h t e n the bolts to 30-35 foot-pounds torque.

(1) Place the inner thrust washer over the

( 5 ) Install the front balance weights (fig.

forward end of the idler gear hub with the flat in

3-55).

t h e inner diameter of the thrust washer over

the flat on the end of the gear hub, and the oil

( 6 ) Attach the gear nut retainer plates to

the gears with bolts and lockwashers and

g r o o v e s in the thrust washer facing the idler

tighten the bolts to 35-39 foot pounds torque.

gear.

( 7 ) Check the clearance between the thrust

(2) Place the small protruding end of the

w a s h e r and the gear on both shafts. The clear-

i d l e r gear hub through the end plate and into

ance should be 0.0080.015 inch, or a maximum

t h e counterbore in the cylinder block.

of 0.019 inch with used parts.

(3) Insert two 3/8-inch-16 bolts through the

( 8 ) Check the backlash between the mating

idler gear hub and thread them into the cylinder

gears. The backlash should be 0.0030.005 inch

block, as shown in figure 3-57, to be sure the bolt

and should not exceed 0.007 inch between used

h o l e s will be in alignment when the flywheel

h o u s i n g is installed.

gears.

(4) Insert the 3/8-inch-16 by 1 3/4-inch special

(9) Install the flywheel housing (para 3-22).

bolt through the center of the idler gear hub and

(10) Install the cylinder head (para 3-19).

thread it into the cylinder block. Tighten bolt to

(11) Install the engine (para 2-5).

30-35 foot pounds torque. Then, remove the two

3-30. Idler Gear Assembly

3 / 8 - i n c h - 1 6 bolts previously installed for align-

a. General. The engine idler gear and bearing

ment of the gear hub.

assembly, located at the flywheel end of engine,

( 5 ) Lubricate the idler gear hub and idler

meshes with the camshaft and crankshaft

g e a r bearings liberally with clean engine oil.

g e a r s , and rotates on a stationary hub. The hub

( 6 ) Position the crankshaft gear and cam-

is secured directly to the cylinder block by a bolt

s h a f t gear or balance shaft gear so that their

that passes through the hub, and three bolts

m a t c h m a r k s will align with those on the idler

that pass through the flywheel housing, hub,

gear.

a n d end plate.

( 7 ) With these matchmarks in alignment,

b. R e m o v a l .

install the idler gear, as shown in figure 3-58.

(1) Remove flywheel housing (para 3-22).

( 8 ) Apply a thin film of cup grease to the

( 2 ) Refer to figure 3-56 and remove idler

i n n e r face (face with oil grooves) of the outer

g e a r assembly.

i d l e r gear thrust washer. The, place the thrust

c. Cleaning y Inspection, and Repair.

washer over the end of the idler gear hub with

(1) Clean the idler gear and bearing assem-

t h e oil grooves in side of thrust washer facing

bly, hub, and thrust washers thoroughly. Use

the idler gear, and the flat in the inner diameter

cleaning solvent P-D-680, or equal and dry

of thrust washer over the flat on the end of the

t h o r o u g h l y . Examine gear teeth and bearing for

i d l e r gear hub.

s c o r i n g , pitting, and wear. If gear teeth are

( 9 ) Install the idler gear hole spacer.

worn or bearing is scored, pitted or worn exces-

(10) Install the flywheel housing (para 3-22).

sively, the gear and bearing and bearing assem-

3-31. Crankshaft Main Bearing

bly must be replaced, or a new bearing installed

a. General. The main bearing shells are of

i n the gear. Also, examine the outside diameter

p r e c i s i o n type and are readily replaceable with-

o f the idler gear hub and thrust washers for

o u t machining. They are used at each journal

being scored and worn. If the thrust washers or

3-68