An axle nut socket is a tool used to remove the axle nut on front-wheel drive as well as certain four-wheel drive vehicles. This enables the wheel hub to be separated from the axle. These types of vehicles commonly use a splined axle to be tightened into the wheel hub by the axle nut, requiring a specially-designed axle nut socket to remove the nut. Some axle nut socket designs resemble a common socket wrench. Other versions used with ratcheting axle nuts, such as those used on some Ford pickup trucks, require a special socket with small fingers extending away from the socket body.
The design of the typical front-wheel drive axle involves the use of the axle nut to firmly hold the drive axle inside of the front wheel hub. This axle is splined and fits snugly inside of a similarly-splined wheel hub to prevent the wheel hub from slipping on the axle as power is applied to drive the vehicle. The axle nut socket is required to remove the axle nut when servicing the wheel bearing, axle or constant velocity (CV) joint. Once the axle nut has been removed, it often requires the use of a wheel hub puller to separate the hub from the axle spline.
Regardless of the size of the axle nut socket, most manufacturers of the tool do not recommend using an impact wrench to loosen the axle nut. A simple breaker bar is commonly all that is required to loosen and remove the nut with an axle nut socket. For a stubborn axle nut, a spray with a rust-penetrating oil is usually all that is needed to persuade the nut to break loose. Occasionally, a very rusty nut will require repeat applications of the penetrating fluid, along with an overnight soak.
Some versions of the axle nut socket use a small locating point inside of the socket to locate the tool squarely on the axle nut. Most axles have a slight depression machined into the center of the axle shaft where the shaft was positioned onto the lathe points. By placing the axle nut socket locating point in this depression, the tool user is assured that the socket is placed squarely on the nut. This prevents slippage of the socket that could result in stripped threads on the axle shaft or a stripped axle nut. The axle nut socket should only be used to remove axle nuts, as damage could result in the tool from using it on other types of bolts or nuts.