The rear axle assembly is hypoid, and for semi-floating type, the centerline of the pinion gear is below that of the ring gear, and this enables the differential to allow the outer rear tyre to rotate at a faster rate than the inner one when turning. It is build onto the axles which are splined to the differential side gears, so the inner tire turns its side gear slower than the outer tire, the differential pinion gears roll round the slower side gear to drive the outer side gear and tire more quickly. This differential is located inside another metal casing commonly referred to as the carrier, which is made of pressed steel, comes with an axle tubes made of pressed steel and welded at appropriate areas. 4WD units are provided with independently assembled front axle incorporating a differential and a pair of drive axles having inner as well as out Eric Constant Velocity (CV) joints. One design of limited slip uses a locking component at the rear axle which is only locked when a wheel loses traction; clutch cones slow down rotation of the differential case where one wheel has good grip and the other has poor grip, equalizing the rotation speed of the axleshaft that drives the good wheel. One should always look for other possibilities as noise originating from the axle could be due to any other reason and sometimes tire noise could be due to worn or low pressure tires. Other forms of noise may also be misleading; therefore sounds such as engine and transmission noise need to be isolated by noting the engine speed and the running of the engine in neutral can assist in determining of the problem is from the axle. As a rule, a do-it-yourselfer will find it uneconomical to rebuild the differential because requiring special tools, and for replacing the axleshaft, oil seal, bearing or total removal of the differential for its repair or replacement is suggested which should in reality be referred to dealer service department or a qualified repair shop. If the rear axle has to be replaced, there is identification code and manufacturer's code imprinted on the front side of the right rear axle tube giving the rear axle ratio, differential type, manufacturer, and the date built so that the correct axle is acquired.