Final Drive Fundamentals and Service (Off-Road)

Question 1

1. Identify two (2) functions of a final drive system.
   a)
   b)

Answer 1

1. Provide a means of gaining additional powertrain torque multiplication.
   b) Absorb shock loads imposed on the powertrain due to operation in harsh off-road environments.

Question 2

2. Which of the following can be used in off-road equipment final drive systems?
   a) sprockets and chains
   b) planetary gear sets
   c) two gear single reduction assemblies
   d) four gear double reduction assemblies
   e) any of the above can be used in a final drive system

Answer 2

2. e) any of the above can be used in a final drive system

Question 3

3. Planetary final drive systems can be identified as inboard mounted or outboard mounted.
   a) true
   b) false

Answer 3

3. a) true

Question 4

4. Explain what is meant by the term outboard mounted, when describing planetary final drive systems.

Answer 4

4. The term outboard mounted refers to the location of the planetary final drive system.
   An outboard mounted planetary final drive is positioned at the wheel or sprocket when tracked machines are considered. The final drive system is located some distance from the bevel gear assembly; well outside the bevel gear/differential housing or machine frame.

Question 5

5. List one possible disadvantage of an inboard mounted final drive.

Answer 5

5. The size of the output components must increase substantially to manage the increased output torque of the final drive.

Question 6

6. The final drive housings on many motor graders act very similar to which component
of an on-highway truck?
a)   torque rod
b)   leaf spring
c)   transverse rod
d)   walking beam

Answer 6

6. d) walking beam

Question 7

7.   On wheeled equipment, the most common gearing configuration used in single
planetary final drives is a:
a)   first speed reverse.
b)   first speed reduction.
c)   second speed reverse.
d)   second speed reduction.

Answer 7

7. b) first speed reduction.

Question 8

8. Chain drives are typically simpler in design and more cost effective to produce and operate than comparable gear boxes.
   a) true
   b) false

Answer 8

8. a) true

Question 9

9. The inverter phase module converts:
   a) AC to DC for the traction motors in propel mode.
   b) DC to AC during dynamic braking.
   c) DC to AC for the traction motors in propel mode.
   d) AC to DC from the generator to the DC bus.

Answer 9

9. c) DC to AC for the traction motors in propel mode.

Question 10

10. The choppers control the amount of current flow through the:
    a) generator rotor as part of the field excitation.
    b) traction motors during dynamic braking.
    c) DC bus in propel mode.
    d) resistive grids during dynamic braking.

Answer 10

10. d) resistive grids during dynamic braking.

Question 11

11. A low DC bus voltage must be verified prior to working in which areas of an AC
    drive system?
    a) the inverter cabinet
    b) the traction motor axle box
    c) the blower motor
    d) all areas which are exposed to high voltage

Answer 11

11. d) all areas which are exposed to high voltage

Question 12

12. What are the two(2) layers of gloves that must be worn when working on high
    voltage systems?
    a) rubber inner and leather outer gloves
    b) leather inner and rubber outer gloves
    c) nitrile inner and rubber outer gloves
    d) rubber inner and nitrile outer gloves

Answer 12

12. a) rubber inner and leather outer gloves

Question 13

13. What is the minimum safe working distance for a technician wearing full PPB when testing a system for high voltage?
    a) 0 cm(0”) the technician is wearing full PPB so he is protected from the high
    voltage
    b) 30 cm(12”)
    c) 45 cm(18”)
    d) 80 cm(30”)

Answer 13

13. b) 30 cm (12”)

Question 14

14. Tracked equipment may be equipped with the following types of final drive systems:
    a) spur gear, single reduction.
    b) planetary gear, single reduction.
    c) spur gear, double reduction.
    d) planetary gear, double reduction.
    e) any of the above responses are possible.

Answer 14

14. e) any of the above responses are possible.

Question 15

15. Two gears in mesh can be used as a final drive gear reduction system. Which ofthe
    following relationships must be true in order to achieve a gear reduction?
    a) A large diameter gear drives a small diameter gear.
    b) Both gears in mesh are of equal diameters.
    c) A small diameter gear drives a large diameter gear.
    d) Two gears in mesh cannot achieve a gear reduction, an idler must be used.

Answer 15

15. c) A small diameter gear drives a large diameter gear.

Question 16

16. When a planetary final drive is used on a tracked machine, the last gear reduction is between the drive sprocket and the track chain.
    a) true
    b) false

Answer 16

16. b) false

Question 17

17. Clean lubricant and cleanliness during the level check and lubricant filling process will greatly extend the life of final drive components.
    a) true
    b) false

Answer 17

17. a) true

Question 18

18. Final drive components may be lubricated by splash and/or pressure lubrication systems.
    a) true
    b) false

Answer 18

18. a) true

Question 19

19. Sometimes a drive sprocket on a crawler must be removed before you can access the final drive components. When you pull the sprocket off the drive hub with a hydraulic press, you must ensure the sprocket does not fly across the shop when it pops free. The service manual will explain this safety process.
    a) true
    b) false

Answer 19

19. a) true