The rear axle assembly comprises a live rear axle. Drive to rear wheels through hypoid bevel gears, two pinion differential and semi-floating axle shafts using taper roller bearings. A malleable cast-iron hypoid housing with pressed in steel tubes and a pressed steel rear cover.
The crown wheel and pinion ratio (often known as the diff ratio) equates to 3.08:1.
This is arrived at by the number of teeth (37) on the crown wheel divided by the number of teeth (12) on the pinion giving a figure of 3.08.
This was the only ratio offered for the TR8, including the automatic version, giving the car a balance between speed, acceleration and fuel consumption.
As the casing is identical to that of the TR7, two other "diff ratios" could be used from the TR7, namely, 3.90:1 and 3.45:1, by merely swapping axles. However, this would upset the overall balance of the car. A further ratio, 2.84:1, can be found in the Rover SD1 Vitesse but would involve a complete strip and rebuild of both axles and a great deal of technical expertise.