An axle carrier is known by many names, such as chunk, differential and third member, each describing the component of a drive axle that houses the gear set. The axle carrier can be either removable or designed and cast into the axle housing depending on the type and style of the axle. When working with a removable carrier, the gear set can be accessed by sliding the drive axles out of the differential and removing the carrier. When working with a non-removable carrier, the rear cover is removed from the differential to access the gear set.
The pinion gear, ring gear and spider gears are all housed within the axle carrier. Commonly made from heavy cast iron, some performance carrier designs are made from aluminum to reduce unsprung weight from the axle. Some racing applications also use a spool to eliminate the spider gears and the heavy, factory-designed positive traction unit within the carrier, creating a lighter-weight option in the critical drive line component. Gear lube is used in the axle housing to lubricate the gear set. Seals positioned in the axle tubes retain the lube inside of the carrier.
To remove a removable carrier from an axle housing, the first step is to drain the lubrication into a catch pan. The axles must be removed next by loosening the bearing retaining plate located behind the axle flange and sliding the axles out of the housing. Once the attaching bolts are removed from the carrier, it can be removed from the axle housing. Any servicing required can be performed with the carrier on a bench for added convenience. On a vehicle with a non-removable carrier design, service to the unit is commonly completed with the axle in the vehicle.
The removable axle carrier is preferred in most motorsports due to the ability to bring several different carriers to the track, each set up with a different gear ratio set. This allows easy gearing changes to aid the crew in setting the race car up for the proper track conditions. The most common style of carrier is manufactured using a Ford Motor Company design and is used in virtually every type of motorsport around the world. Favored for its strength and ease in swapping the axle carrier, the Ford design is the choice of race teams and powerful street car builders when building a bullet-proof axle that will withstand extreme amounts of horsepower and torque.