Question 1

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?

Accepted Answer

Technician A is correct because replacing a failed differential carrier with a rebuilt/exchange unit is indeed a common practice in truck repair facilities today, as it can be more cost-effective and time-efficient than overhauling the unit in-house. Technician B is also correct because measuring shim pack thickness during disassembly can greatly speed up the reassembly process, ensuring that the differential is reassembled correctly and efficiently.

Question 2

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

Accepted Answer

75W gear lube has the lowest viscosity rating among the options, making it more fluid at lower temperatures and thus better suited for severe winter conditions. Lower viscosity lubricants flow more easily at cold temperatures, ensuring better protection and lubrication of gears during cold starts.

Question 3

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

Accepted Answer

The answer of What is the most common cause of...

Question 4

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

Accepted Answer

The "W" in the viscosity rating stands for "Winter" and indicates the oil's flow characteristics at cold temperatures. A lower number before the "W" indicates better flow at colder temperatures. Therefore, 75W would have the best flow characteristics at 10 degrees Fahrenheit compared to the other options.

Question 5

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?

Accepted Answer

Technician B is correct because typically, the highest oil fill hole on an axle is the standard location for checking and filling differential oil to ensure the proper oil level is maintained. Technician A's statement about differential carriers having two oil fill holes at different levels and the use of a specific hole based on pinion angle is not a common practice in automotive maintenance.

Question 6

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?

Accepted Answer

The answer of Technician A says that Roadranger CD-50 meets...

Question 7

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

Accepted Answer

Drilling out the rivets with a bit that is 1/32 inch (0.8 mm) smaller than the rivet size is the correct method. This allows for the removal of the rivet without enlarging the hole or damaging the parts being disassembled.

Question 8

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?

Accepted Answer

The answer of Technician A says that mixing synthetic oil...

Question 9

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

Accepted Answer

The answer of What is used to lubricate the wheel...

Question 10

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?

Accepted Answer

Both Technician A and Technician B are correct. A spinout condition can indeed cause immediate failure in components such as the power divider or the differential carrier, as stated by Technician A. Additionally, Technician B is correct in stating that a spinout condition can also lead to geartrain damage that might not cause a breakdown immediately but can lead to issues later on.

Question 11

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

Accepted Answer

The answer of Which of the following gear lubes suitable...

Question 12

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

Accepted Answer

Using a thinner spacer will increase the preload on the pinion bearing, bringing it up to the specified value.

Question 13

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?

Accepted Answer

The answer of Technician A says that a differential carrier...

Question 14

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?

Accepted Answer

Technician B is correct because after changing the differential carrier oil, jacking up each side of the axle ensures that the lubricant reaches the wheel ends. Technician A is incorrect because most heavy trucks do not have hub inspection windows for checking lube levels.

Question 15

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?

Accepted Answer

Technician A is correct because checking the lube level at the banjo housing fill hole when the pinion angle exceeds 7 degrees ensures proper lubrication under altered geometry. Technician B's method is not standard practice for differential maintenance.

Question 16

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

Accepted Answer

A dial indicator is the correct tool for measuring both crown gear runout and pinion to crown gear runout because it can precisely measure small distances and is capable of detecting minute variations in surface height or alignment, which is essential for these types of measurements.

Question 17

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

Accepted Answer

Pinion bearing preload is measured by attaching a cord and fish scale to a pinion bearing, as this setup allows for the measurement of the force required to rotate the pinion bearing, indicating the preload on the bearing.

Question 18

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

Accepted Answer

Used gear lube should be disposed of through a recycling refiner, as it can be processed and re-refined into new lubricating products, reducing environmental impact and conserving resources.

Question 19

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?

Accepted Answer

Technician B is correct because API GL-5 lubricant is indeed extreme pressure (EP) rated and designed for use in hypoid gearsets, which are commonly found in the differentials of vehicles. Technician A is incorrect because there is no API GL-6 specification; the API GL-5 is the relevant specification for such applications.

Question 20

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?

Accepted Answer

Technician A is correct because the MIL L 2105D specification is indeed equivalent to the API GL-5 specification, which is commonly used for heavy-duty differential gear oils. Technician B is also correct because API GL-3 and GL-4 lubricants are generally not approved for use in current heavy truck differential carriers due to their lower levels of extreme pressure (EP) additives compared to API GL-5, which is required for the higher load conditions experienced in these applications.

Quiz 24: Heavy-Duty Truck Axle Service and Repair