Operation of Live Front Axles

Wheeled Vehicle Drive Lines, Axles, And Suspension Systems
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the rear axles on the vehicle.

None of the front axle assemblies used in wheeled vehicles are designed to be operated

under power all of the time. Some vehicles have a control in the cab that permits the

driver to engage the front axle when it is needed. Other vehicles have a device made into

the transfer assembly to automatically engage the front-wheel drive when the rear tires

lose traction and spin.

When the vehicle is traveling straight ahead, both the inner and outer axle shafts are on

the same line. If the front axle is engaged to the power train, the inner axle shaft will

drive the CV joint. The CV joint will, in turn, drive the outer axle shafts which are

splined to the wheel hubs. As steering arms and rods turn the knuckles, the axle shafts

will flex at the CV joint.

During turns, the CV joint will continue to deliver a smooth, steady flow of torque. The

steering linkage moves both steering knuckles at the same time to the proper angle for the

turn.

LUBRICATION OF LIVE AXLES

Whenever the vehicle is moving, the gears of the final drive and differential are turning.

The lower part of the gearbox is filled with gear oil to a required level. The lower part of

the gearing passes through a pool of oil each time the unit rotates and thereby lubricates

all the working parts.

On some types of axle assemblies, oil flows down each axle shaft housing to lubricate the

bearings that support the outer ends of the axle shafts or wheel bearings.

Lubrication of the CV joints is generally done by packing the joints with GAA (grease,

automotive and artillery).