Deck 24: Heavy-Duty Truck Axle Service and Repair

Question 1

Technician A says that synthetic lubricants may be used in truck differential carriers but OEMs have yet to authorize extended oil drain intervals.Technician B says that using synthetic gear lubes is cost effective compared to mineral-base gear lube because of greatly increased oil drain intervals and reduced labor.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Answer 1

B

Question 2

Which of the following is required practice when refilling a differential carrier housing with lube after an oil change?

A) fill with an API GL-5 rated lubricant to the bottom of the filler hole
B) add an additional 2 pints (1 liter)to the power divider fill hole
C) jack the axle sequentially at either end to ensure lube reaches the wheel ends
D) all of the above

Answer 2

D

Question 3

Technician A says that one reason OEMs have eliminated the initial (break-in)lube drain on a new or rebuilt differential carrier is improved machining precision of current geartrain components.Technician B says that because synthetic gear lubes have superior ability to suspend abrasive contaminants,OEMs no longer require a break-lube change.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Answer 3

C

Question 4

The lubricant classification that meets the American Petroleum Institute (API)standard for heavy truck differential carriers is known as:

A) GL-4
B) GL-5
C) GL-6
D) GL-7

Question 5

Where would you usually find the AXLE IDENTIFICATION numbers on a rear axle carrier housing?

A) stamped into the banjo housing
B) metal tag attached to the banjo housing
C) both A and B
D) neither A nor B

Question 6

Which of the following best describe an ideal ring gear tooth contact pattern for a new crown and pinion gearset?

A) centered between the root and top land
B) covers 1/2 or more of the length of the ring gear teeth
C) contact pattern closer to the toe than the heel
D) all of the above

Question 7

Which of the following types of axle shaft failures would likely produce a relatively smooth,flat fracture pattern?

A) shock load
B) fatigue
C) lubrication failure
D) constant torque overload

Question 8

When replacing a damaged crown and pinion gearset,the damaged pinion cone (PC)variation number was +2,and the new PC variation number is specified as -5.If the original shim pack thickness measured 0.030-inch (0.76 mm),what should the new shim pack thickness be?

A) .033-inch (0.84 mm)
B) .037-inch (0.94 mm)
C) .023-inch (0.58 mm)
D) .027-inch (0.69 mm)

Question 9

A truck differential carrier is noisy when cornering.Which of the following would be the more likely cause?

A) pinion bearings worn
B) low axle lube level
C) damaged differential pinion gears
D) worn carrier bearings

Question 10

When correcting a pinion to crown gear tooth contact pattern that is too far from the toe,what adjustment should be made?

A) move the pinion gear toward the ring gear
B) move the ring gear to decrease backlash
C) move the pinion gear away from the ring gear
D) move the ring gear to increase backlash

Question 11

Which of the following are indications of fatigue-type failures in gear components?

A) pitted and spalled tooth surfaces
B) star-shaped fracture
C) scalloped fracture pattern
D) all of the above

Question 12

Where is a spigot bearing located in a differential carrier assembly?

A) end of each axle shaft
B) on each differential spider
C) hub the crown gear
D) pinion gear shaft

Question 13

Which of the following would indicate that the lube level in a differential carrier housing was acceptable?

A) oil level is exactly even with the bottom of the filler hole
B) lube level pours out the filler hole when the plug is removed
C) lube level is one knuckle joint below the filler hole
D) lube level is within two knuckle joints below the filler hole

Question 14

Which of the following types of failures can result in some components becoming blackened and discolored?

A) fatigue
B) lubrication breakdown
C) shock-load
D) all of the above

Question 15

What properties are associated with synthetic gear lubes when compared with mineral based lubricants?

A) better lubricity
B) higher boil temperatures
C) better boundary lubrication
D) all of the above

Question 16

What is the area of a ring gear tooth that is furthest from the center known as?

A) toe
B) heel
C) root
D) face

Question 17

When is the BEST time to drain differential carrier oil on a scheduled lube change?

A) when it has cooled to ambient temperature
B) at operating temperature
C) after cooling for one hour
D) any time on a summer's day

Question 18

When correcting a pinion to crown gear tooth contact pattern that is too close to the top land and off-center,how should you make an adjustment?

A) move the pinion gear toward the ring gear
B) move the pinion gear away from the ring gear
C) move the ring gear to increase backlash
D) move the ring gear to decrease backlash

Question 19

A fractured axle shaft with a star-shaped fracture pattern indicates that the cause of the failure is related to:

A) bending stress
B) torsional stress
C) shock load
D) lubrication failure

Question 20

Which of the following could be produced by a spinout failure?

A) broken gear teeth
B) broken axle shaft
C) overheated power divider
D) all of the above

Question 21

Technician A says that it is common practice today in truck repair facilities to replace a failed differential carrier with a rebuilt/exchange unit rather than to overhaul the unit in-house.Technician B says that when rebuilding differential carriers,it is good practice to measure shim pack thickness on disassembly because it usually speed reassembly times.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 22

Which of the following gear lube viscosity ratings would best suit severe winter conditions?

A) 75W
B) 80W-90
C) 80W-140
D) 85W-140

Question 23

What is the most common cause of lubrication-related failures of differential carriers?

A) contaminated lube
B) underfilled rear axle housings
C) lube breakdown
D) mixing lubricants

Question 24

Which of the following gear lube viscosity ratings would indicate an oil that would possess the best flow characteristics at 10 degrees Fahrenheit?

A) 75W
B) 80W-90
C) 80W-140
D) 90W-140

Question 25

Technician A says that most differential carriers have two oil fill holes at different levels and that the pinion angle off a horizontal plane determines which fill hole should be used..Technician B says that the oil fill hole that is highest on an axle should always be used to check oil level.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 26

Technician A says that Roadranger CD-50 meets the API GL-5 standard.Technician B says that an advantage of using a synthetic gear lube such CD-50 is that it can all but eliminate spinout failures.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 27

When disassembling a riveted crown gear and flange case half,how should the rivets be removed?

A) drill out with bit 1/32 inch (0.8 mm)larger than rivet size
B) chisel and cold punch
C) drill with bit 1/32 inch (0.8 mm)smaller than rivet size
D) press with 10 ton (9 metric-ton)press and cold punch

Question 28

Technician A says that mixing synthetic oil with mineral base lube can cause premature lubricant breakdown due to incompatible additives.Technician B says that a good way of avoiding mixing of lubes in differential carriers is to write the gear lube required into memory in one of the data bus modules.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 29

What is used to lubricate the wheel bearings in a heavy truck drive axle assembly?

A) wheel end grease
B) axle grease
C) gear lube in an isolated hub
D) gear lube in differential carrier housing

Question 30

Technician A says that a spinout condition can result in an immediate failure in either the power divider or the differential carrier.Technician B says that a spinout condition can cause geartrain damage that does not result in a breakdown until sometime later.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 31

Which of the following gear lubes suitable for use in a differential carrier is rated to have the longest service life?

A) any GL-5
B) any GL-6
C) TranSynd
D) CD-50

Question 32

After measuring pinion bearing preload,the preload value measures less than specified.Which of the following steps is required?

A) use a thinner spacer
B) use a thicker spacer
C) increase pinion yoke torque
D) decrease pinion yoke torque

Question 33

Technician A says that a differential carrier thrust screw should be adjusted to the point that it just contacts the thrust block or crown gear.Technician B says that if a thrust screw was to be backed out all the way,the thrust block would drop into the carrier housing.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 34

Technician A says that the lube levels in drive axles on most heavy trucks can be checked by viewing through a hub inspection window.Technician B says that following a differential carrier oil change,each side of the axle should be in turn,be jacked up and held for one minute to ensure that lube gets to the wheel ends.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 35

Technician A says that when a differential carrier pinion angle exceeds 7 degrees,lube level should be checked at the banjo housing fill hole.Technician B says that when correcting the lube level in differential carrier housings,the best way is to remove both fill plugs and pump oil into the fill plug at the side of the carrier until it begins to spill from the fill hole in the banjo housing.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 36

Which of the following tools could be used to measure both crown gear runout and pinion to crown gear runout?

A) thickness gauges
B) depth micrometer
C) fish scale
D) dial indicator

Question 37

When you attach a cord and fish scale to a pinion bearing,what are you about to measure?

A) pinion to crown gear backlash
B) pinion bearing preload
C) pinion bearing endplay
D) crown bearing turning resistance

Question 38

How should used gear lube be disposed of from a service facility?

A) toxic waste disposer
B) recycling refiner
C) pour down any drain with a separator
D) use as gravel dust settling agent

Question 39

Technician A says that API GL-6 lubricant supercedes GL-5 and should be used in all current differential carriers.Technician B says that API GL-5 is extreme pressure (EP)rated for use in hypoid gearsets.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 40

Technician A says that the military gear lube classification MIL L 2105D is equivalent to API GL-5.Technician B says that API GL-3 and API GL-4 are not approved for use in current heavy truck differential carriers.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 41

Technician A says that when rebuilding a differential carrier,a crown and pinion gearset can often be reused.Technician B says that when either a crown or pinion gear have been diagnosed defective,they should both be replaced as a matched unit.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 42

The rear wheels on a tandem drive axle will not turn but the drive axle to the rear differential carrier does turn.Which of the following should you do FIRST?

A) pull the power divider
B) pull the forward differential carrier
C) pull the rear differential carrier
D) pull both rear axle half-shafts