Week #5 - Final Drive (Chapters 23, 24)

Question 1

What is the function of a rear drive axle on a truck?

a. It supports the weight of the truck and its load
b. It redirects the torque from the driveshaft to the drive wheels
c. It provides gear reduction necessary to drive the vehicle
d. all of the above

Answer 1

d. all of the above

Question 2

What gear sets would determine the output gear ratio in a single-reduction rear axle carrier?

Answer 2

The pinion and crown gear set

Question 3

What is the usual way of supporting a differential carrier input shaft in front of the pinion?

Answer 3

Opposed tapered roller bearings

Question 4

What is the correct method for removing rivets from a crown gear assembly?

Answer 4

Use a drill and punch

Question 5

True or False: A single wheel spinout on a tandem drive tractor can destroy a carrier assembly by shocking the gearing when the spinning wheel finds traction.

Answer 5

True

Question 6

Spinout failures are unavoidable during winter operation

Answer 6

False

Question 7

A spinout condition can cause a lubrication failure of a final drive carrier.

Answer 7

True

Question 8

What measuring tool should be used to check crown gear runout?

Answer 8

A dial indicator

Question 9

True or False: The rear wheels on a tandem drive axle truck will not turn but the drive shaft does, so you will need to pull both axle shafts.

Answer 9

True

Question 10

What gear lube viscosity rating is usually recommended for use in a differential carrier for a truck operating in temperatures of -30°F (-34°C)?

Answer 10

An EP-rated lubricant

Question 11

True or False: The tooth contact pattern can be moved closer to the root by increasing the crown gear backlash.

Answer 11

False

Question 12

Which of the following would be a factor in defining the reduction ratio in differential carrier gearing?

a. the number of teeth on side gears
b. the number of teeth on differential pinions
c. the number of splines on side gears
d. the number of teeth on crown gear

Answer 12

d. the number of teeth on crown gear

Question 13

Which of the following best describes the two axles on a standard tandem trailer?

a. dead axles
b. drive axles
c. lift axles
d. steer axles

Answer 13

a. dead axles

Question 14

What gear sets performs the first reduction in a double-reduction differential carrier?

Answer 14

The pinion and crown gear set

Question 15

True or False: Crown gear backlash is correctly adjusted by alternately loosening and tightening the bearing adjusting rings.

Answer 15

True

Question 16

What is the correct method for fitting a crown gear to a flange case half?

Answer 16

Heat in a water tank to 170°F (77°C)

Question 17

In which of the folloiwng axles would you be likely to find a planetary gearset?

a. lift axles
b. double-reduction differential carrier
c. trailer axles
d. single-reduction differential carrier

Answer 17

b. double-reduction differential carrier

Question 18

True or False: Pinion spiders walk at any time there is differential action.

Answer 18

True

Question 19

What pinion and crown gear arrangement positions the pinion gear below the centerline of the crown gear?

Answer 19

c. hyboid (hypoid gearset is commonly used on the forward drive axle of a tandem drive)

Question 20

What is the most common method of managing an interaxle differential lockout device?

a. spring-engaged, electrically released
b. spring-engaged, pneumatically released
c. pneumatically engaged, spring-released
d. hydraulically engaged, spring-released

Answer 20

c. pneumatically engaged, spring-released

Question 21

Which of the following whould indicate that the level was correct when checking lube oil level in a differential carrier housing with the fill plug removed.

a. oil level within 1 inch (2.5 cm) of the fill hole
b. oil level within one finger joint of the fill hole
c. oil level exactly even with the bottom of the fill hole
d. oil spilling from the fill hole

Answer 21

c. oil level exactly even with the bottom of the fill hole

Question 22

After a differential carrier overhaul, what method would best ensure that the wheel bearings receive proper initial lubrication?

Answer 22

Jack the axle up at each side for 1 minute, then level and check the fill hole level.

Question 23

True or False: A truck is producing some rear axle noise that can be heard only during turns, so the problem is probably excessive backlash between the drive pinion and the crown/ring gear.

Answer 23

False

Question 24

True or False: Spinout failures are often caused by a defect in the interaxle differential gearing.

Answer 24

False

Question 25

When planning to drain and replace the lubricant in a differential carrier, which of the following is preferred? a. flush with solvent b. flush with kerosene c. drain when the lubricant is at operating temperature d. drain after allowing to cool overnight

Answer 25

c. drain when the lubricant is at operating temperature

Question 26

Which of the following restricts normal differential action except during cornering? a. double-reduction differential b. two-speed axles c. no-spin locking differentials d. controlled traction differential

Answer 26

c. no-spin locking differentials

Question 27

Which of the following pavement surfaces would fit the description of a split coefficient surface? a. wheels on right side in gravel, wheels on driver side on pavement b. driving the tractor in snow c. wheels on both sides of tractor on low friction coefficient surface d. wheels on both sides of tractor on high friction coefficient surface

Answer 27

a. wheels on right side in gravel, wheels on driver side of pavement

Question 28

In a tandem axle power divider, what component drives the helical gear set?

Answer 28

The input shaft

Question 29

In which of the following differentials would you find friction plates alternately splined to a driver and tanged to the gear support case? a. two-speed tandem axles b. controlled traction differentials c. no-spin locking differentials d. all of the above

Answer 29

b. controlled traction differentials

Question 30

True or False: A tag axle on a highway tractor is located in front of a drive axle or axles.

Answer 30

False

Question 31

When a truck is traveling in a straight-ahead direction, which of the following should be true? a. Differential action is required b. Differential pinions do not turn on the spider shafts c. Differential pinions walk on the spider shafts d. Differential side gears do not turn.

Answer 31

b, Differential pinions do not turn on the spider shafts

Question 32

True or False: A truck is producing some rear axle noise that can be heard only during turns, so the likely cause of the problem is excessive backlash between the side gears and the differential pinions.

Answer 32

True

Question 33

When a gear tooth separates, leaving a smooth, flat fracture pattern, what is the usual cause?

Answer 33

Single shock load

Question 34

True or False: Most OEMs recommend extended rear axle oil drain intervals when synthetic lubricants are used.

Answer 34

True

Question 35

What gear combination accommodates a speed difference between the two drive wheels ona drive axle?

Answer 35

The differential pinions and side gear

Question 36

True or False: During differential action on a drive axle in a turn, the speed increase on the outboard wheel has to be inversely proportional to the speed decrease on the inboard wheel.

Answer 36

True

Question 37

True or False: The differential carrier should be flushed with kerosene at every oil change.

Answer 37

False

Question 38

What pinion and crown gear arrangement positions the pinion gear above the centerline of the crown gear?

Answer 38

Amboid (amboid gearset is commonly used on the rear drive axle of a tandem drive)

Question 39

A pusher axle is located behind a drive axle.

Answer 39

False

Question 40

What type of failure is usually indicated when a shaft fails, producing a star-shaped fracture pattern?

Answer 40

Torsional failure

Question 41

What type of bearing is used as a pilot/spigot for supporting a differential carrier input shaft behind the pinion?

Answer 41

Opposed tapered roller bearings

Question 42

True or False: The rear wheels on a tandem drive axle truck will not turn but the drive shaft does, so the first step is to pull the forward differential carrier.

Answer 42

False