Axle

Types of Drive Axle Assembly

Rigid Axle

  • The axle housing holds the axle shafts.

  • It also supports the weight of the vehicle.

  • Brake and suspension parts attach to the axle housing.

  • The axle housing, differential, and axle shafts move together as one unit.

  • Common on trucks and heavy-duty vehicles.

  • Strong and durable, but gives a rougher ride than independent suspensions.

Independent Axle

  • The axle housing is mounted solidly to the vehicle’s chassis.

  • Each wheel has its own drive axle shaft.

  • The axle shafts connect to the wheels using U-joints or CV joints.

  • Each wheel can move up and down independently.

  • This design gives better stability and a smoother ride on uneven roads.

Components of the Axle Assembly

Axle Shafts

  • Found inside the horizontal tubes of the axle housing.

  • Transfer power from the differential to the drive wheels.

  • Rotate with the wheels to move the vehicle.

  • Key part of the driveline system that delivers engine torque to the road.

Differential Assembly

  • Contains the drive pinion and ring gear set along with the differential case 

  • Includes two pinion gears and two side gears

  • Rotates the axle shafts at varying speeds during vehicle cornering

Axle Housing

  • A one-piece housing with two tubes extending from each end.

  • Houses and supports the components of the axle assembly.

  • Contains mounts or attachments for the axle bearings.

  • The center section is usually made of cast iron or aluminum.

  • The steel tubes on each side support the axle shafts.

Bearings

  • A typical axle assembly has:

    • Pinion bearings

    • Differential case side bearings

    • Axle bearings

  • Pinion Bearings:

    • Support the drive pinion gear.

    • Help keep the gear aligned with the ring gear.

  • Differential Case Side Bearings:

    • Support the differential case.

    • Allow the differential to rotate smoothly inside the axle housing.

  • Axle Bearings:

    • Support the axle shafts.

    • Help carry the weight of the vehicle.

U-joints

  • Double-hinged mechanical devices.

  • Located at both ends of the driveshaft.

  • Transmit power from one shaft to another at fixed or changing angles.

  • Allow the driveshaft to move with the suspension while still turning smoothly.

  • When greater angles are needed, the axle shafts use CV (constant velocity) joints instead of U-joints.

Types of Axle Housing

Integral Carrier Housing

  • Also called a Salisbury axle.

  • The differential assembly is accessed through a removable rear cover.

  • The ring gear and differential assembly can be removed as a unit from the housing.

  • The pinion gear, however, must be serviced inside the housing — it is not removable as part of the carrier.

  • Commonly used in modern rear axle designs due to simplicity and structural strength.

Removable Carrier Housing

  • Also called a Banjo-style housing or dropout carrier.

  • The ring and pinion gear set can be removed from the housing as a single unit.

  • The carrier assembly (often called the third member or pumpkin) bolts to the front of the axle housing.

  • The rear of the housing is solid, unlike the Salisbury type, which has a removable rear cover.

  • Commonly used in trucks and performance vehicles for easier servicing of internal gears.

Types of Axle Shafts

Semi-Floating

  • The bearing is located just inside the axle housing.

  • The axle shaft supports the vehicle’s weight in addition to transmitting torque.

  • The axle shaft itself connects directly to the wheel hub and carries both driving torque and vehicle load.

  • Commonly used in light trucks and rear-wheel-drive (RWD) passenger cars.

semi-floating

Three-quarter Floating

  • The bearing is mounted on the outside of the axle housing.

  • The bearing supports the wheel hub, which is bolted to the end of the axle shaft.

  • The axle shaft supports part of the vehicle’s weight, while the rest is transferred through the wheel hub and bearing to the axle housing.

  • Provides a balance between strength and simplicity but does not completely isolate the axle shaft from vehicle load.

  • Commonly found on older passenger cars and trucks before more advanced designs became standard.

Three-quarter floating

Full-floating

  • Two bearings are mounted on the outside of the axle housing to support the wheel hub.

  • The wheel hub, not the axle shaft, supports the vehicle’s weight.

  • The axle shaft’s sole purpose is to transfer torque from the differential to the wheel hub.

  • Commonly used in medium and heavy-duty trucks due to high strength and durability.

  • This design prevents axle shaft failure from causing wheel separation.

Full-floating

Fluid Level Check

When checking the fluid level, check if:

  • The axle is level

  • The fluid is even with the bottom of the filler plug opening

Maintenance Procedure of the Drive Axle Assembly

Step 1

  • First, place the drain pan under the differential.

Step 2

  • Next, remove all the bolts, leaving the top cover bolt loose.

Step 3

  • Gently pry away the lower area of the cover and drain the fluid.

Step 4

  • Once the fluid is drained, remove the differential cover and clean the gasket material from the housing and cover.

Step 5

  • Use a shop towel to remove the metal debris stuck to the magnet

  • Check the areas around the bolt holes for dimples

  • Use a ball peen hammer to straighten the areas around the holes, if needed

Step 6

  • Apply the sealant to the sealing surface of the differential cover.

Step 7

  • Reinstall the differential cover and then torque all the bolts.

Step 8

  • Finally, add new fluid through the fill plug and then reinstall the fill plug.