Question 1

Front axle disconnect systems are being discussed. Technician A says the systems use a vacuum motor to disengage and engage the right side axle shaft from the differential. Technician A says an electric motor is used to engage and disengage the axle. Who is correct?

Accepted Answer

Both technicians are correct. Some front axle disconnect systems use a vacuum motor to engage and disengage the axle, while others use an electric motor.

Question 2

Two technicians are discussing the difference between 4WD and AWD. Technician A says AWD does not have an interaxle differential lockout. Technician B says AWD does not have a low range. Who is correct?

Accepted Answer

Technician B is correct that AWD does not have a low range. However, Technician A is incorrect in saying that AWD does not have an interaxle differential lockout. Some AWD systems do have interaxle differential lockouts, which allow for better traction and stability in certain situations.

Question 3

Technician A says in a full-time AWD transmission/transfer case, the hydraulic clutch that controls slippage in the 4WD system is controlled by inputs from the ABS wheel speed sensors. Technician B says some full-time AWD transfer cases can lock the differential so that the front and rear driveshafts must turn at the same speed. Who is correct?

Accepted Answer

Technician A is correct because in many full-time AWD systems, the hydraulic clutch that manages power distribution (and thus controls slippage) between the front and rear axles indeed receives input from the ABS wheel speed sensors. This helps the system to dynamically adjust the power distribution based on the traction conditions detected by the wheel speeds. Technician B is also correct because some full-time AWD systems have the capability to lock the center differential (or equivalent mechanism), ensuring that the front and rear driveshafts rotate at the same speed, which is particularly useful in low-traction situations to ensure equal power distribution to all wheels.

Question 4

Locking hubs are generally found on ______.

Accepted Answer

Locking hubs are typically used on older SUVs and pickup trucks with part-time 4WD systems. Full-time all-wheel-drive vehicles and newer SUVs and pickup trucks with full-time 4WD systems typically do not require locking hubs.

Question 5

If the 4WD indicator light is flashing on and off, ______.

Accepted Answer

A flashing 4WD indicator light typically indicates that a fault code is stored in the 4WD system. It is recommended to have the system diagnosed by a professional to determine the specific issue.

Question 6

Interaxle differentials are being discussed. Technician A says the interaxle differential is located inside the front axle housing. Technician B says the interaxle differential is located inside the rear axle housing. Who is correct?

Accepted Answer

Neither technician is correct. An interaxle differential is typically located in the transfer case, which is mounted between the front and rear axles in a four-wheel drive system.

Question 7

A ratcheting sound from an automatic locking hub may be caused by ______.

Accepted Answer

A ratcheting sound from an automatic locking hub is often caused by the hub on the opposite side of the axle not disengaging properly, leading to improper engagement and noise.

Question 8

Many transfer cases require _____ lubricants as used in differentials and in some manual transmissions.

Accepted Answer

Many transfer cases are subjected to high torque loads and extreme conditions, which require a lubricant with extreme pressure (EP) additives. EP lubricants are designed to withstand high pressure between gear teeth and provide protection against wear and gear scuffing. Synthetic lubricants and low viscosity lubricants may also be suitable for some transfer cases, but EP lubricants are the best choice for maximum protection. Polycarbonate is not a type of lubricant and is not used in transfer cases.

Question 9

Automatic locking hubs are unlocked when ______.

Accepted Answer

The answer of Automatic locking hubs are unlocked when ______.
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Question 10

Technician A says the viscous clutch is filled with silicone fluid. Technician B says the viscous clutch solenoid is controlled by inputs from the wheel speed sensors. Who is correct?

Accepted Answer

Technician A is correct because a viscous clutch indeed uses silicone fluid to transfer torque based on the difference in rotational speed between two shafts. Technician B is incorrect because a viscous clutch does not use a solenoid for its operation; it operates based on the shear strength of the silicone fluid and does not require electronic control from wheel speed sensors.

Question 11

Technician A says part-time 4WD vehicles do not have an interaxle differential. Technician B says part-time 4WD vehicles do not have a transfer case. Who is correct?

Accepted Answer

Technician A is correct because part-time 4WD vehicles typically do not have an interaxle differential, which allows for different speeds between the front and rear axles. This is why they should not be driven on dry pavement in 4WD mode, as it can cause driveline bind. Technician B is incorrect because part-time 4WD vehicles do have a transfer case, which is used to engage and disengage the 4WD system.

Question 12

Technician A says mismatched tire sizes can cause transfer case noise. Technician B says incorrect tire inflation pressure can cause transfer case noise. Who is correct?

Accepted Answer

Both technicians are correct. Mismatched tire sizes can cause transfer case noise because different tire sizes rotate at different speeds, causing strain on the transfer case. Incorrect tire inflation pressure can also cause transfer case noise because it affects the overall diameter of the tire, leading to different rotational speeds between tires and causing strain on the transfer case.

Question 13

Part-time 4WD is found on what type of vehicle?

Accepted Answer

The answer of Part-time 4WD is found on what type...

Question 14

Technician A says the transfer case uses a chain to transfer torque from the transmission to the front driveshaft. Technician B says the transfer case uses spur or helical cut gearsets to transfer torque to the front driveshaft. Who is correct?

Accepted Answer

Transfer cases can use either a chain or gearsets (spur or helical cut) to transfer torque from the transmission to the front driveshaft, making both Technician A and Technician B correct.

Question 15

Technician A says AWD systems are based on FWD systems that use a viscous clutch, center differential, or transfer clutch to transfer power from the transaxle to a rear driveline. Technician B says an AWD system is based on RWD systems that use a transfer case, front drive shafts, and front axle assemblies to drive the front wheels. Who is correct?

Accepted Answer

AWD systems can be based on either FWD or RWD systems, but Technician A is correct that they typically use a viscous clutch, center differential, or transfer clutch to transfer power from the transaxle to a rear driveline. Technician B is incorrect in stating that AWD systems are based on RWD systems that use a transfer case, front drive shafts, and front axle assemblies to drive the front wheels.

Question 16

Technician A says on-demand 4WD systems are controlled by the PCM/TCM. Technician B says when slip is detected at the rear wheels, the duty cycle to the output clutch at the transfer case is decreased. Who is correct?

Accepted Answer

Technician A is correct because on-demand 4WD systems are indeed often controlled by the vehicle's Powertrain Control Module (PCM) or Transmission Control Module (TCM), which manage the distribution of power to the wheels based on various inputs. Technician B is incorrect because when slip is detected at the rear wheels, the duty cycle to the output clutch at the transfer case is typically increased, not decreased, to send more power to the front wheels to regain traction.

Question 17

Which of the following components is (are) NOT found in a transfer case?

Accepted Answer

Blocking rings are typically found in manual transmissions, not in transfer cases.

Question 18

The wheel bearing locknuts on most 4WD vehicles require the use of a ______.

Accepted Answer

Most 4WD vehicles require a four- or six-pronged special socket to properly engage and tighten or loosen the wheel bearing locknuts.

Question 19

What will happen if the manual locking hubs remain in the 4WD or locked position when the vehicle is driven in 2WD mode?

Accepted Answer

When manual locking hubs are left in the locked position while driving in 2WD mode, it causes the front drivetrain components to rotate unnecessarily, leading to reduced fuel economy and increased driveline noise.

Question 20

Technician A says wheel bearings on 4WD vehicles are permanently sealed and lubricated and do not require disassembly and service after the hubs have been submerged in water. Technician B says a frequent cause of wheel bearing failure is the use of oversized tires mounted on wheels with substantial offset. Who is correct?

Accepted Answer

Technician A is incorrect because wheel bearings on 4WD vehicles are not permanently sealed and can still be damaged by water. Technician B is correct because using oversized tires with substantial offset can cause added stress on the wheel bearings and lead to failure.

Quiz 44: Four- and All- Wheel Drive