401g Transfer Case and Auxiliary Drives

Question 1

On a short wheel based vehicle, what drivetrain equipment is used to drive the front driving axle?

a) a transfer case
b) a special inter-axle differential assembly
c) a transmission with front and rear output shafts
d) a gear system off of the front of the engine

Answer 1

b) a special inter-axle differential assembly

Question 2

State the function of the transfer case.

Answer 2

The transfer case receives torque from the main or auxiliary transmission. It then passes that torque on to the rear driving axles and forward to the front driving axle.

Question 3

What type of lubrication do transfer cases utilize?

Answer 3

The internal transfer case components are generally lubricated by a splash type of lubrication system. Many transfer cases are also equipped with a positive displacement oil pump as part of the lubrication system.

Question 4

Transfer cases are only available in one configuration with an option to disengage the drive to the front axle.
T/F

Answer 4

false; Transfer cases come in many different configurations and with several options. They can vary from a simple two shaft, single speed design with no ability to disengage the front drive shaft (full-time all wheel drive) to a four shaft, two speed design with the ability to disengage the front drive, offer a neutral and two speed ranges, a differential assembly and include a power takeoff.

Question 5

The mechanism that gives the operator the ability to disengage the torque to the front drive axle is called the:

a) axle separator.
b) limiting clutch.
c) front splitter.
d) front axle declutch

Answer 5

front axle declutch.

Question 6

On a transfer case with more than one range option, high range is typically an overdrive (0.74:1).
T/F

Answer 6

false; The high range selection is generally a direct drive (1:1), while the low range provides a gear reduction (typically about 2:1 to 2.5:1).

Question 7

What device does a full-time transfer case use to prevent driveline windup?

a) planetary gear set
b) typical differential assembly
c) limited slip clutch pack
d) windup clutch

Answer 7

planetary gear set

Question 8

A transfer case mounted power takeoff cannot receive more torque than the engine can develop.
T/F

Answer 8

false; Since this power takeoff is situated after the main transmission, it is able to receive varying amounts of torque. This is dependent on the gear selected in the main transmission at the time.

Question 9

Explain the procedure used to check the oil level in the transfer case.

Answer 9

To check the oil level, clean the dirt away from the area surrounding the filler plug to prevent the accidental contamination while checking the level. The oil must be level with the bottom of the filler plug opening.

Question 10

What could cause oil to be lost out the breather?

Answer 10

If either the range shift cylinder, front axle declutch cylinder or the power takeoff shift cylinder O-rings are leaking, the housing is put under excessive pressure. The rapid air venting can cause airborne oil particles to be pulled out the breather.

Question 11

Excessive noise and vibration from the transfer case can be caused by:

a) excessive driveline angles
b) excessive transfer case bearing endplay
c) operating on good surface with declutch engaged
d) all of the above

Answer 11

d) all of the above.

Question 12

When removing the transfer case, it is critical that the mounting location of the drivelines be clearly marked.
T/F

Answer 12

true

Question 13

One of the vital concerns with the transfer case assembly is:

a) housing concentricity
b) input shaft timing
c) output shaft timing
d) bearing endplay

Answer 13

d) bearing endplay

Question 14

Which types of auxiliary drive systems are always driving any time the engine is turning?

a) front engine mounted
b) rear engine mounted
c) transfer case mounted
d) drop box
e) auxiliary transmission mounted
f) transmission mounted power takeoff

Answer 14

• front engine mounted

- rear engine mounted

Question 15

What must the operator do before engaging the power takeoff?

a) shut the engine off
b) stop the transmission countershaft from turning
c) first engage the component that the power takeoff is powering
d) raise the engine to governed rpm

Answer 15

b) stop the transmission countershaft from turning

Question 16

On the air actuated power takeoff system, what is the air routed through before going to the air valve?

a) pressure protection valve
b) pressure regulator valve
c) flow control valve
d) the shift cylinder

Answer 16

a) pressure protection valve

Question 17

The indicator light for the power takeoff system is activated by an engagement switch located in the shift valve.
T/F

Answer 17

false; The engagement switch is a normally open or a normally closed switch mounted on the shift cover.

Question 18

What precautions must be taken to properly match a power takeoff to an application and prevent equipment damage?
(4)

Answer 18

• Always refer to the appropriate catalogue, service literature and owner’s manual(s). Follow the manufacturer’s recommendations when selecting, installing, repairing or operating a PTO.
• Never attempt to use a PTO that is not specifically recommended by the PTO manufacturer for the vehicle transmission.
• Always match the PTOs specified output capabilities with the requirements of the equipment to be powered.
• Never use a power takeoff whose speed range could exceed the maximum safe operating speed of the equipment to be powered.

Question 19

What two (2) functions do the gaskets between the power takeoff and the transmission provide?
(2)

Answer 19

• Act as a seal to keep lubrication from leaking between the two mating surfaces
• Provide a way of setting the proper backlash between the PTO input gear and the PTO drive gear of the transmission

Question 20

PTO backlash must be measured between:

a) the PTO input gear and the PTO output gear.
b) the PTO input gear and the idler.
c) the PTO input gear and the transmission drive gear.
d) the transmission drive gear and the transmission input gear.

Answer 20

c) the PTO input gear and the transmission drive gear.

Question 21

When installing an adapter housing, it is only necessary to adjust the gear backlash between the adapter housing and the transmission drive gear.
T/F

Answer 21

false; When installing an adapter housing, proper backlash must be established between the transmission drive gear and the adapter housing gear as well as between the adapter housing gear and the PTO input gear.

Question 22

If the power takeoff is installed with insufficient backlash, the complaint will be:

a) gear clatter.
b) gear whine.
c) sheared keys.
d) housing breakage

Answer 22

b) gear whine

Question 23

When installing the repaired power takeoff, it is acceptable to install it without measuring backlash if the same number and thickness of gaskets that were originally removed are used.
T/F

Answer 23

false; Carefully check and adjust the gear backlash as part of the installation process. Do not assume that the proper backlash will be obtained by installing the same number and thickness of gaskets that were originally on the vehicle. The backlash adjustment must be done very carefully and re-checked after the fasteners are torqued.