401h Drive Axle Assembly Fundamentals (On-Road)

Question 1

List the four (4) functions of the drive axle assembly.

Answer 1

• The drive axle assembly must withstand and support the weight of the vehicle and load that has been passed through the suspension system to the drive axle assemblies.
• The drive axle assembly provides the last gear reduction in the basic vehicle powertrain.
• The drive axle assembly must change the direction of torque by 90°.
• The drive axle must transfer torque evenly between the two wheel assemblies it is driving while allowing for a difference in speed between the two.

Question 2

The weight rating that refers to how much each axle can carry is called the:

Answer 2

gross axle weight rating (GAWR).

Question 3

The gross combination weight rating refers to the:

Answer 3

total combined gross axle weight ratings for a vehicle and its trailers.

Question 4

The reason a driving axle would be added to the rear of a truck rather than a non-driving (tag or pusher) would be to:

Answer 4

increase traction.

Question 5

The percentage of grade at which a drivetrain system can start a loaded vehicle moving at idle is called:

Answer 5

startability.

Question 6

Which components are attached to the drive axle housing?

a) suspension components
b) wheels tires and hubs
c) carrier housing
d) all of the above

Answer 6

d) all of the above.

Question 7

The main function of the carrier housing is to:

Answer 7

hold the internal gear components.

Question 8

The pinion bearing cage is always a removable component of the carrier housing.
T/F

Answer 8

false; It may be a removable piece of the carrier housing or an integral component.

Question 9

The overhung pinion differs from the straddle mount in that it has a short stub that extends past the end of the pinion gear.
T/F

Answer 9

false; The overhung mount pinion can be distinguished by the flat surface at the end of the pinion gear. A short stub shaft that extends past the end of the pinion gear characterizes the straddle mount pinion design.

Question 10

The input drive pinion is in constant mesh with the:

Answer 10

bevel gear.

Question 11

What is the main purpose of the thrust screw?

Answer 11

The thrust screw prevents the bevel gear from deflecting away from the input pinion during heavy torque loads.

Question 12

The bevel gear is bolted directly to the:

a) carrier housing.
b) differential pinions.
c) plain case half.
d) flanged case half.

Answer 12

d) flanged case half.

Question 13

The differential pinions are driven by the:

a) cross shafts.
b) axle side gears.
c) bevel gear.
d) case halves.

Answer 13

a) cross shafts.

Question 14

The most common differential carrier assembly used today is the:

a) single speed single reduction.
b) single speed double reduction.
c) two speed double reduction.
d) planetary carrier.

Answer 14

a) single speed single reduction.

Question 15

Number the following components in the path-of-power through the single speed single reduction carrier assembly. Begin with the input shaft yoke and end with the wheel assemblies.
input yoke \_\_\_\_\_\_\_\_\_\_\_\_\_
differential cross shaft \_\_\_\_\_\_\_\_\_\_\_\_\_
differential case \_\_\_\_\_\_\_\_\_\_\_\_\_
axle shafts \_\_\_\_\_\_\_\_\_\_\_\_\_
input drive pinion \_\_\_\_\_\_\_\_\_\_\_\_\_
bevel gear \_\_\_\_\_\_\_\_\_\_\_\_\_
axle side gears \_\_\_\_\_\_\_\_\_\_\_\_\_
differential pinions \_\_\_\_\_\_\_\_\_\_\_\_\_
wheel assemblies \_\_\_\_\_\_\_\_\_\_\_\_\_

Answer 15

input shaft yoke           1
differential cross shaft 5
differential case           4
axle shafts                    8
input drive pinion         2
bevel gear                    3
axle side gears             7
differential pinions       6
wheel assemblies        9

Question 16

On a two speed double reduction carrier assembly, the component that drives the helical drive gear is the:

a) cross shaft.
b) bevel gear.
c) helical driven gear.
d) shift collar.

Answer 16

d) shift collar.

Question 17

In the planetary differential carrier assembly, low gear is achieved when:

a) the sun gear is locked to the retainer plate.
b) the sun gear is locked to the carrier.
c) the carrier is locked to the bevel gear.
d) the bevel gear is locked to the internal gear.

Answer 17

a) the sun gear is locked to the retainer plate.

Question 18

The torque available to the wheel with good traction in a wheel spin condition is:

Answer 18

d) the same as the torque to the spinning wheel.

Question 19

When a vehicle is turning a corner, the differential assembly allows the:

a) inner drive wheel to rotate faster than the outer drive wheel.
b) outer drive wheel to rotate faster than the inner drive wheel.
c) bevel gear to rotate at the same speed as the outer drive wheel.
d) bevel gear to rotate at the same speed as the inner drive wheel.

Answer 19

b) outer drive wheel to rotate faster than the inner drive wheel.

Question 20

The inter-axle differential is physically located:

a) between the front and rear drive axle assemblies.
b) in the front drive axle assembly.
c) in the rear drive axle assembly.
d) in the driveline before the front drive axle assembly.

Answer 20

b) in the front drive axle assembly.

Question 21

The input shaft drives the helical drive gear through a set of splines.
T/F

Answer 21

false; The input shaft drives the differential shaft through a set of splines.

Question 22

The cross shafts of the inter-axle differential are driven by the:

a) case halves.
b) helical drive gear.
c) differential pinions.
d) input shaft.

Answer 22

d) input shaft

Question 23

The lockout assembly of the inter-axle differential locks what two components?

a) input shaft and cross shaft
b) input shaft and helical drive gear
c) helical drive gear and the output haft
d) input shaft and the inter-axle differential case

Answer 23

b) input shaft and helical drive gear.

Question 24

Semi-floating axle shafts can be removed from a vehicle when the weight of the vehicle is on the drive wheels.
T/F

Answer 24

false; To remove the semi-floating axles, the vehicle weight must be supported and the drive wheels must be off the ground.

Question 25

On a drive axle assembly using a planetary final drive system, the input member of the planetary system is the:

Answer 25

sun gear

Question 26

Identify the two (2) main drive axle lubrication systems.

Answer 26

• splash lubrication

- combination splash and pressure lubrication

Question 27

Explain the drive axle filtration systems.

Answer 27

The drive axle assemblies use magnetic drain plugs, magnetic screens and spin on filters to filter and clean the oil.

Question 28

A differential assembly equipped with a no-spin assembly allows for normal differential action when the vehicle turns a corner.
T/F

Answer 28

true

Question 29

When the operator activates the driver controlled differential lock, the operator is mechanically locking:

a) the axle shafts together.
b) the two case halves together.
c) the differential pinions to the axle side gears.
d) one axle shaft to the differential case.

Answer 29

d) one axle shaft to the differential case.