Heavy-Duty Drive Axle Assemblies

A tandem drive axle model is designated as DS404-P. Using the identification codes, what is the nominal Gross Axle Weight Rating (GAWR) per tandem in pounds?

4,000 pounds 10,000 pounds 40,000 pounds 400,000 pounds

A carrier assembly has two gear reductions. The first reduction ratio (input pinion to bevel gear) is 2.5:1, and the second reduction ratio (helical pinion to helical driven gear) is 2.0:1. What is the overall gear ratio through this carrier assembly?

0.5:1 2.5:1 5.0:1 4.5:1

In a standard differential under good traction conditions, the total torque received by the differential case assembly is 4067.4 Nm (3000 lb-ft). If the torque is divided equally, how much torque is sent to each axle shaft?

1016.85 Nm (750 lb-ft) 1355.8 Nm (1000 lb-ft) 2033.7 Nm (1500 lb-ft) 4067.4 Nm (3000 lb-ft)

A planetary two-speed drive axle assembly has a crown gear set ratio of 3.5:1 and a planetary gear set ratio of 1.5:1 (Double Reduction in Low). What is the overall gear ratio when the assembly is operating in Low Speed?

2.33:1 3.5:1 5.0:1 5.25:1

A drive axle assembly has a crown gear with 48 teeth and a drive pinion with 10 teeth. What is the final drive gear ratio?

0.20:1 4.00:1 4.80:1 5.80:1

A drive axle assembly has a crown gear with 39 teeth and a drive pinion with 11 teeth. What is the final drive gear ratio? Round to two decimal places.

3.55:1 3.73:1 3.91:1 4.10:1

In a differential wheel spin condition, the crown gear is turning at 100 rpm and the axle shaft on one side is stopped (0 rpm). According to the differential action principle, what speed must the opposite axle wheel turn?

50 rpm 100 rpm 200 rpm 300 rpm

In an inter-axle differential spin-out condition, the forward drive axle pinion is stationary. If the inter-axle differential cross shaft is rotating at 500 rpm, what speed would the rearward drive axle pinion be spinning due to differential action?

500 rpm 750 rpm 1000 rpm 250 rpm

Which gear arrangement term describes a drive pinion that meshes with its crown (bevel) gear above the centerline of the crown gear?

Hypoid Straddle mount Amboid Spiral bevel

A straddle mount pinion design, which is characterized by a pilot bearing surface extending past the end of the pinion gear, is more common on applications that experience:

Low revolutions per minute (rpm) rates. High torque loads. Single-speed single reduction. Tridem axle arrangements.

What is the fundamental requirement when replacing a drive pinion and crown gear set?

They must be individually balanced and installed with new thrust washers. The pinion depth must be adjusted using the pinion bearing preload spacer. They must be used in matched sets as they are designed together. They must utilize the largest possible diameter crown gear.

The Gross Axle Weight Rating (GAWR) is the manufacturer's rating that dictates the construction of the housing, bearings, and wheel ends based on the weight the axle must:

Propel (Torque transfer). Safely carry (Load support). Transfer during a full-floating configuration. Maintain in a low-speed ratio.

When all of the individual Gross Axle Weight Ratings (GAWR) for a vehicle are added together, they establish the total weight of the vehicle and its load, which is known as the:

Tare Weight. Gross Combination Weight Rating (GCWR). Gross Vehicle Weight Rating (GVWR). Axle Speed Sensing Rating (ASSR).

What is the primary functional difference between a live axle and a dead axle?

A live axle is found on tandem arrangements; a dead axle is found on tridem arrangements. A live axle propels the vehicle; a dead axle strictly carries the load. A live axle always uses a planetary two-speed carrier; a dead axle uses a single-speed reduction. A live axle uses semi-floating shafts; a dead axle uses full-floating shafts.

What is the critical action that must occur to remove a semi-floating axle shaft from a vehicle, compared to a full-floating axle shaft?

The axle must be locked by the differential lock. The rear cover must be removed first. A drive wheel must be raised off the ground before a semi-floating axle shaft can be removed. The gear oil must be drained from the axle housing.

What is the main function of the full-floating axle shaft?

To carry the weight of the vehicle and cargo. To transmit braking and cornering forces. To drive the wheel and hub assembly. To support the drive axle housing.

If a heavy-duty truck has a tandem or tridem drive axle arrangement, what component must be added to transmit power from one drive axle to the next?

A planetary two-speed axle assembly. A speed sensing unit. An inter-axle differential assembly. A standard differential case.

What is the primary characteristic of a single-speed single reduction carrier assembly?

It provides two separate gear reductions. It uses helical gears for the final reduction. It offers only one path-of-power and one gear reduction through the drive pinion and crown gear. It uses an outboard planetary final drive.

In a single-speed double reduction carrier assembly, the second gear reduction is accomplished through a set of:

Hypoid gears. Straight spur gears. Helical gears. Spiral bevel gears.

What is the common name given to the component that houses the bearings supporting the drive pinion, and may be a removable piece of the carrier housing?

Differential Housing Pinion Bearing Cage Differential Case Half Ring Gear Mount Assembly

What component is used as a selective spacer to determine the pinion bearing preload in the pinion cage assembly?

Pinion position shims Drive pinion nut Pinion preload spacer Outer pinion bearing cup

What design feature characterizes an overhung mount input drive pinion when viewed from the side?

A pilot bearing surface that extends past the end of the gear. A flat surface at the end of the pinion gear (flat pinion face). It meshes with the crown gear below the centerline. It uses three sets of tapered roller bearings.

Why is a special thrust screw and jam nut sometimes used on drive axle assemblies?

To adjust the backlash between the differential side gears. To help prevent the crown gear from deflecting away from the pinion during high torque load. To provide a mounting surface for the differential bearing adjuster. To secure the pinion bearing cage to the carrier housing.

The differential case assembly is composed of two halves (a flanged and a plain) that are bolted together and supported by which type of bearing on either end?

Ball bearings Straight roller bearings Tapered roller bearings Pilot bushings

The crown gear is bolted to which specific component in the differential case assembly?

The plain case half The differential cross shaft The flanged differential case half The differential side gear

The differential cross shaft, often called the spider, is connected to and driven by:

Splines on the axle shaft. The differential pinion gears. Recesses machined into the differential case halves. The ring gear bolts.

What components are placed between the differential pinion gears and the differential case assembly?

Pinion position shims Thrust washers Bearing adjuster rings Spring retainers

The axle side gears are the final components in the differential case assembly and mate with the splines on each axle shaft. The axle side gears are in mesh with which other gears?

The crown/ring gear The differential pinion gears The helical drive gear The input pinion

If a vehicle equipped with a standard differential is turning a corner, what is the differential's function concerning torque delivery?

Torque is increased to the wheel on the outside of the turn. Torque is transferred entirely to the wheel with the most traction. Torque is always divided equally between the two drive wheels. Torque is reduced to compensate for the difference in wheel speeds.

The No-Spin traction control unit replaces which standard differential components?

The ring gear and differential case. The axle side gears and axle shafts. The standard cross shaft, differential pinions, and axle side gears. The differential case halves and the spider.

In a No-Spin unit during normal locked operation, what component remains stationary relative to the rotating spider and driven clutch members?

The outer drive axle shaft. Nothing; all parts rotate at the same speed. The spring retainer. The holdout ring.

What condition causes the driven clutch in a No-Spin unit to disengage (overrun) when a vehicle is turning a corner?

The inner wheel rotates faster than the spider. The outer wheel travels faster than the inner wheel and has enough traction to drive the outer driven clutch faster than the spider. The operator applies the service brake. The spring pressure on the clutch plates is eliminated.

What is the normal noise that occurs during the cornering process of a vehicle equipped with a No-Spin unit?

A grinding sound indicating pinion gear failure. A steady howl indicative of backlash problems. A ratcheting noise due to the disengaging and engaging of the clutching teeth. A squealing noise caused by poor lubrication.

A Driver-Controlled Axle Differential Lock allows the operator to mechanically connect which two components together when poor traction is encountered?

The drive pinion and the differential case. The axle shaft on one side and the differential case. The shift collar and the rear axle housing. The differential side gear and the crown/ring gear.

The Eaton driver-controlled wheel lock is typically operated by the driver using which two types of systems?

Hydraulic pressure or vacuum actuation. Mechanical cable or direct linkage. Air switch or an electric-over-air system. Torsional spring or centrifugal weights.

Which heavy-duty application often requires the use of an Outboard Planetary Final Drive system?

Highway cruising vehicles with high fuel economy ratios. Medium-duty trucks operating primarily on smooth pavement. Heavy-duty trucks transporting heavy loads in an off-road environment. Vehicles with single-speed single reduction carrier assemblies.

In an Outboard Planetary Final Drive system, what is the role of the planetary carrier assembly?

It is the held member (stationary). It is the drive member (input). It is the output member, which is bolted to the hub assembly. It contains the axle side gear and differential pinions.

The internal gear (ring gear) in the Outboard Planetary Final Drive is the held member because it is splined to what fixed component?

The hub assembly. The spindle. The sun gear. The axle shaft.

The Inter-Axle Differential Assembly (Power Divider) is a differential that allows for speed differences to occur between the forward and rearward drive axle input pinions. This assembly is typically an integral part of which axle housing?

The main transmission housing. The rear drive axle assembly. The front or intermediate drive axle assembly. The dead axle assembly.

When the inter-axle differential is allowed to operate (lockout disengaged), how is torque divided between the two drive axle assemblies (forward and rearward)?

Torque is transferred entirely to the axle with the most traction. Torque is divided unevenly, favoring the forward axle. Torque is divided equally between the two drive axle assemblies. Torque transfer is stopped entirely.

What is the functional result of mechanically locking out the inter-axle differential (lockout engaged)?

The inter-axle differential action is temporarily eliminated, and the entire assembly turns as a solid unit. The torque is diverted entirely to the rearward drive axle. The truck enters a freewheeling condition. The differential pinions rotate at maximum speed.

Under what driving condition is it CAUTIONED against locking out the inter-axle differential?

Moving straight ahead at low speed on a slippery surface. Operating the truck on dry roads or turning the truck. Slowly approaching a stretch of road where traction is poor. When the torque load applied is momentarily broken by easing off the throttle.

Which type of gear oil classification (API rating) is required for hypoid gear sets?

GL1 GL3 GL5 GL6

What is the fundamental disadvantage of mixing different types of gear oil in a drive axle housing?

The lubricant's viscosity rating will increase dramatically. Mixing different types of gear oil causes a breakdown chemically. The oil will resist foaming under extreme temperature. The SAE designation will automatically change.

The full synthetic gear lubricants offer which specific benefit over traditional gear oils?

They maintain a lower cost per litre. They reduce bearing and gear distress only at high temperatures. They reduce bearing and gear distress under extreme operating conditions (high and low temperatures). They are resistant to oxidation but not to corrosion.

The vast majority of drive axle assemblies are lubricated using which basic system?

Dedicated pressure pump and filter system. Fluid transfer pump system. Splash lubrication system, where the crown gear moves through an oil reservoir. Combination pressure/gravity feed system.

Why do some manufacturers install a lube pump in the front or intermediate differential carrier assemblies on a tandem axle combination?

To ensure the pinion bearings receive adequate lubrication when the axle is cold. To offer lubrication to the inter-axle differential assembly that cannot be reached by splash lubrication, especially during a wheel spin. To provide a high-pressure oil flow to the wheel ends. To continuously filter the gear oil using a magnetic drain plug.

If the differential is equipped with an oil pump, what filtration component is installed on the pickup to trap materials before the pump ingests them?

Spin-on oil filter Magnetic screen Dedicated drain plug Oil trough

When the drive pinion nut fails, which selective component must be recommended as a related sale?

Pinion position shim Differential cross shaft Crush sleeve Differential gear

If a customer is ordering a remanufactured drive axle unit, what essential information must the parts technician relay to the customer regarding the old unit?

That all parts are guaranteed to be new and carry a lifetime warranty. That the customer will be charged a core charge and must return the old axle assembly (core) to receive a credit. That the unit will be shipped without bearings and seals. That the unit must be custom rebuilt as the supplier has no units in stock.