Subaru Impreza WRX STi differential

What is a differential?

 A differential is necessary to drive a pair of wheels while allowing them to rotate at different speeds. A vehicle with two drive wheels has the problem that when it turns a corner the drive wheels must rotate at different speeds to maintain traction and prevent tire degradation. In vehicles without a differential, such as go-karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism.

What problem does a differential solve?

When turning a corner, the inner wheel travels a shorter distance than the outer wheel, so without a differential either the inner wheel rotates too quickly or the outer wheel rotates too slowly, which results in difficult and unpredictable handling, damage to tires and roads, and strain on (or possible failure of) the drivetrain. In rear-wheel drive automobiles the central drive shaft (or prop shaft) engages the differential through a hypoid gear (ring and pinion). The ring gear is mounted on the carrier of the planetary chain that forms the differential. This hypoid gear is a bevel gear that changes the direction of the drive rotation.

Open differentials and ABS units

Many newer vehicles feature traction control, which tries to mitigate the poor traction characteristics of an open differential by using the anti-lock braking system to limit or stop the slippage of the low traction wheel, increasing the torque that can be applied to the opposite wheel. While not as effective as a traction-aided differential, it is better than a simple mechanical open differential with no traction assistance.

Subaru Impreza WRX STi differentials

The Subaru Impreza WRX STi is built from 1994 to 2014 and consists of 5 generations, with 1 different fuel types and 4 different body shapes. When requesting a part, it is important that you choose the correct version.