Yamaha YFM45FAR, YFM450FAR. Service Manual

DRIV

CHAPTER 7.

DRIVE TRAIN

.................................................................................. 7-1

FRONT CONSTANT VELOCITY JOINTS AND DIFFERENTIAL GEAR

REMOVING THE UNIVERSAL JOINT .................................................. 7-9
REMOVING THE RING GEAR  ............................................................. 7-9
CHECKING THE CONSTANT VELOCITY JOINT  .............................. 7-10
CHECKING THE DIFFERENTIAL GEAR  ........................................... 7-10
CHECKING THE GEAR MOTOR ........................................................ 7-11
ASSEMBLING THE FRONT CONSTANT VELOCITY JOINT  ............ 7-11
ASSEMBLING THE DIFFERENTIAL GEAR  ....................................... 7-12
INSTALLING THE UNIVERSAL JOINT  .............................................. 7-13
MEASURING AND ADJUSTING

THE DIFFERENTIAL GEAR LASH ................................................. 7-14

CHECKING THE DIFFERENTIAL GEAR OPERATION ..................... 7-16

REAR AXLE/FINAL DRIVE GEAR AND DRIVE SHAFT

........................... 7-17

REMOVING THE REAR AXLE ........................................................... 7-20
DISASSEMBLING THE FINAL DRIVE GEAR .................................... 7-20
REPLACING THE FINAL DRIVE ROLLER BEARING ........................ 7-21
POSITIONING THE FINAL DRIVE PINION GEAR

AND RING GEAR ............................................................................ 7-22

CHECKING THE REAR AXLE  ............................................................ 7-26
CHECKING THE DRIVE SHAFT  ........................................................ 7-27
CHECKING THE FINAL DRIVE GEAR ............................................... 7-27
MEASUREMENT AND ADJUSTING THE FINAL GEAR LASH  ......... 7-28
ASSEMBLING THE FINAL DRIVE GEAR  .......................................... 7-30
INSTALLING THE FINAL DRIVE GEAR ............................................. 7-30

7 - 1

DRIV

TROUBLESHOOTING

DRIVE TRAIN

TROUBLESHOOTING

The following conditions may indicate damaged shaft drive components:

NOTE:

Areas A, B, and C above may be extremely difficult to diagnose. The symptoms are quite subtle and
difficult to distinguish from normal machine operating noise. If there is reason to believe these
components are damaged, remove the components and check them.

Symptoms

Possible Causes

1.A pronounced hesitation or “jerky” movement

during acceleration, deceleration, or sustained
speed. (This must not be confused with
engine surging or transmission
characteristics.)

2.A “rolling rumble” noticeable at low speed; a

high-pitched whine; a “clunk” from a shaft
drive component or area.

3.A locked-up condition of the shaft drive train

mechanism, no power transmitted from the
engine to the front and/or rear wheel.

A.Bearing damage.

B. Improper gear lash.

C.Gear tooth damage.

D. Broken drive shaft.

E.Broken gear teeth.

F. Seizure due to lack of lubrication.

G.Small foreign objects lodged between the

moving parts.

1.Check:

●

Unusual noises

*****************************************************

The following “noises” may indicate a
mechanical defect:

a.A “rolling rumble” noise during coasting,

acceleration, or deceleration. The noise
increases with front and/or rear wheel speed,
but it does not increase with higher engine or
transmission speeds.
Diagnosis: Possible wheel bearing damage.

b.A

“whining” noise that varies with

acceleration and deceleration.
Diagnosis: Possible incorrect reassembly,
too-little gear lash.

7 - 2

DRIV

TROUBLESHOOTING

CAUTION:

Too little gear lash is extremely destructive to
the gear teeth. If a test ride following
reassembly indicates this condition, stop
riding immediately to minimize gear damage.

c.A slight “thunk” evident at low speed

operation. This noise must be distinguished
from normal machine operation.
Diagnosis: Possible broken gear teeth.

WARNING

Stop riding immediately if broken gear
teeth are suspected. This condition could
result in the shaft drive assembly locking
up, causing loss of control of the machine
and possible injury to the rider.

*****************************************************
2.Check:

●

Drained oil
Drained oil shows large amounts of metal
particles

→

Check the bearing for seizure.

NOTE:

A small amount of metal particles in the oil is
normal.

3.Check:

●

Oil leakage

*****************************************************

Checking steps:

●

Clean the entire machine thoroughly, then
dry it.

●

Apply a leak-localizing compound or dry
powder spray to the shaft drive.

●

Road test the machine for the distance
necessary to locate the leak.
Leakage

→

Check the component housing,

gasket, and/or seal for damage.

Damage

→

Replace the component.

NOTE:

●

An apparent oil leak on a new or nearly new
machine may be the result of a rust-
preventative coating or excessive seal
lubrication.

●

Always clean the machine and recheck the
suspected location of an apparent leakage.

*****************************************************

7 - 3

DRIV

TROUBLESHOOTING

Troubleshooting chart

When basic condition “a” and “b” exist, check the following points:

Elevate and spin both wheels. Feel for
wheel bearing damage.

YES

Replace the wheel bearing.
(Refer to “STEERING SYSTEM” and
“REAR SHOCK ABSORBER AND
SWINGARM” in CHAPTER 8.)

Check the wheel nuts and hub nuts for
tightness.

Torque to specification.
(Refer to “FRONT AND REAR WHEELS”
in CHAPTER 8.)

YES

Check the constant velocity joint. Feel for
bearing damage.

Constant velocity joint bearings and
differential gear bearings are probably not
damaged. Repeat the test or remove the
individual components.

YES

Check the rear brake adjustment.

Adjust per instructions.
(Refer to “ADJUSTING THE REAR
BRAKE” in CHAPTER 3.)

YES

Check the rear axle. Feel for bearing
damage.

Rear axle bearings and rear drive shaft
bearings are probably not damaged.
Repeat the test or remove the individual
components.

YES

Remove the rear axle. Check for axle
bearing damage.

YES

Replace the rear axle bearing.
(Refer to “REAR AXLE/FINAL DRIVE
GEAR AND DRIVE SHAFT”.)

Remove the drive shaft components.

7 - 4

DRIV

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

FRONT CONSTANT VELOCITY JOINTS AND DIFFERENTIAL GEAR

Order

Job name/Part name

Q’ty

Remarks

Removing the front constant
velocity joint and differential gear

Remove the parts in the order below.

Engine skid plate (front)
Front fender

Refer to “SEAT, CARRIERS, FENDERS
AND FUEL TANK” in CHAPTER 3.

Differential gear oil

Drain.

Steering knuckle

Refer to “STEERING SYSTEM” in
CHAPTER 8.

Front arms (lower)

Refer to “FRONT ARMS AND FRONT
SHOCK ABSORBER” in CHAPTER 8.

Brake master cylinder cover

Refer to “FRONT AND REAR BRAKES”
in CHAPTER 8.

Constant velocity joint

Gear motor coupler/on-command four-
wheel drive switch and differential gear
lock switch coupler

1/1

Disconnect.

Differential gear case breather hose

Disconnect.

7 - 5

DRIV

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

Order

Job name/Part name

Q’ty

Remarks

Differential gear

Drive shaft

Compression spring

For installation, reverse the removal
procedure.

7 - 6

DRIV

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

Order

Job name/Part name

Q’ty

Remarks

Disassembling the constant velocity
joint

Remove the parts in the order below.

Circlip

Boot band

Refer to “ASSEMBLING THE FRONT
CONSTANT VELOCITY JOINT”.

Boot band

Dust boot

Circlip

Double off-set joint

Snap ring

Ball bearing

Joint shaft assembly

For assembly, reverse the disassembly
procedure.

7 - 7

DRIV

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

Order

Job name/Part name

Q’ty

Remarks

Disassembling the differential gear

Remove the parts in the order below.

Gear motor/O-ring

1/1

NOTE:

Be sure not to disassemble the gear
motor or remove the pinion gear.

Circlip

Refer to “REMOVING/INSTALLING THE
UNIVERSAL JOINT”.

Bearing

Universal joint

Universal joint yoke/O-ring

1/1

Stopper bolt/shaft

1/1

Shift fork sliding gear

Shift fork

Differential gear case cover

Drive clutch

Shim (left)

7 - 8

DRIV

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

Order

Job name/Part name

Q’ty

Remarks

Differential gear assembly

Shim (right)

Circlip/bearing

1/1

Drive pinion gear

Differential gear case

For assembly, reverse the disassembly
procedure.

7 - 9

DRIV

REMOVING THE UNIVERSAL JOINT

1.Remove:

●

Universal joint

*****************************************************

Removal steps:

●

Remove the circlips

●

Place the U-joint in a press.

●

With a suitable diameter pipe

beneath the

yoke

, press the bearing

into the pipe as

shown.

NOTE:

It may be necessary to lightly tap the yoke with
a punch.

●

Repeat the steps for the opposite bearing.

●

Remove the yoke.

NOTE:

it may be necessary to lightly tap the yoke with
a punch.

*****************************************************
2.Remove:

●

Universal joint yoke
Use a universal joint holder

Universal joint holder:

P/N. YM-04062, 90890-04062

REMOVING THE RING GEAR

1.Remove:

●

Ring gear

NOTE:

The ring gear and the differential gear cover
should be fastened together. Do not
disassemble the differential gear assembly.

CAUTION:

The differential gears are assembled into a
proper unit at the factory by means of
specialized equipment. Do not attempt to
disassemble this unit. Disassembly will
result in the malfunction of the unit.

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

7 - 10

DRIV

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

CHECKING THE CONSTANT VELOCITY
JOINT

1.Check:

●

Double off-set joint spline

●

Ball joint spline

●

Shaft spline
Wear/damage

→

Replace.

2.Check:

●

Dust boots
Cracks/damage

→

Replace.

CAUTION:

Always use a new boot band.

3.Check:

●

Balls and ball races

●

Inner surface of double off-set joint
Pitting/wear/damage

→

Replace.

CHECKING THE DIFFERENTIAL GEAR

1.Check:

●

Gear teeth
Pitting/galling/wear

→

Replace drive pinion

gear and ring gear as a set.

●

Bearing
Pitting/damage

→

Replace.

●

Oil seal

●

O-ring
Damage

→

Replace.

2.Check:

●

Drive shaft splines

●

Universal joints

●

Front drive gear splines
Wear/damage

→

Replace.

●

Spring
Fatigue

→

Replace.

Move the spring up and down.

3.Check:

●

Front drive shaft
Bends

→

Replace.

WARNING

Do not attempt to straighten a bent shaft;
this may dangerously weaken the shaft.

7 - 11

DRIV

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

CHECKING THE GEAR MOTOR

1.Check:

●

Gear motor

*****************************************************

Checking steps:

●

Connect two C size batteries to the gear
motor terminals

. (as shown illustration)

CAUTION:

Do not use a 12 V battery to operate the
pinion gear.

Check that the pinion gear

turns

counterclockwise.

Check that the pinion gear

turns clockwise.

NOTE:

Be sure not to disassemble the gear motor or
remove the pinion gear.

*****************************************************

ASSEMBLING THE FRONT CONSTANT
VELOCITY JOINT

1.Apply:

●

Molybdenum disulfide grease
(into the ball joint assembly)

NOTE:

Molybdenum disulfide grease is included in the
repair kit.

2.Install:

●

Dust boots

●

Dust boot bands

*****************************************************

Installation steps:

●

Apply molybdenum disulfide grease into the
dust boots.

●

Install the dust boots.

●

Install the dust boot bands.

NOTE:

●

The new boot bands may differ from the
original ones.

●

The dust boots should be fastened with the
dust boot bands

at the grooves in the joint

shaft.

*****************************************************

Molybdenum disulfide grease:

40 g (1.4 oz) per dust boot

New

7 - 12

DRIV

FRONT CONSTANT VELOCITY JOINTS AND

DIFFERENTIAL GEAR

3.Check:

●

Free play (thrust movement)
Excessive play

→

Replace the joint

assembly.

ASSEMBLING THE DIFFERENTIAL GEAR

1.Measure:

●

Gear lash
Refer to “MEASURING AND ADJUSTING
THE DIFFERENTIAL GEAR LASH”.

2.Install:

●

Gear motor

*****************************************************

Installation steps:

●

Slide the shift fork sliding gear

, which is

installed to the differential gear, to the left to
put it into the 2WD mode.

●

Connect two C size batteries to the gear
motor terminal

to operate the pinion gear

, and operate it until the paint mark

the gear is aligned with the paint mark

the gear motor case.

CAUTION:

Do not use a 12 V battery to operate the
pinion gear.

●

Insert 8 mm bolts

into the gear motor

and use them as a guide to set the motor on
the differential gear assembly

so that the

shift fork sliding gear

does not move.

CAUTION:

If the position of the shift fork sliding gear
is moved, the position of the differential
gear and the indicator light display may
differ, and the 2WD or differential lock
mode may not be activated.

●

Remove the 8 mm bolts, and then install the
motor with the gear motor bolts.

*****************************************************

Bolts (gear motor)

13 Nm (1.3 m • kg, 9.4 ft • lb)

Yamaha YFM45FAR, YFM450FAR. Service Manual - part 16