The MGC rear axle is a Salisbury tube-type unit, broadly similar to the contemporary MGB's but with several MGC-specific components. The crown wheel and pinion sets use different ratios from the MGB (which used a standard 3.909:1 throughout production), the differential cage is modified to accept the MGC crown wheel and pinion specifications, the propshaft flange is more substantial, and the driving flanges use a sturdier five-stud fixing.
Three Axle Ratios with Exact Change Points
Three crown wheel and pinion ratios were used across MGC production, and the change point is the most important identification detail when ordering a replacement axle or ratio set. Non-overdrive cars used 3.071:1 (14/43 teeth) up to chassis number 4235 (Roadster) and 4265 (GT), changing to 3.307:1 (13/43 teeth) from chassis number 4236 (Roadster) and 4266 (GT). Overdrive cars used 3.307:1 up to the same chassis numbers, changing to 3.7:1 (10/37 teeth) from the same breakpoint. Automatic cars used 3.307:1 throughout production.
The change to the numerically higher 3.7:1 ratio on overdrive cars was one of the most significant improvements made to the MGC during its production run, transforming the car's acceleration and drivability.
Exchange Axle Assemblies
Reconditioned exchange rear axle assemblies are available in all three ratios, in both steel wheel and wire wheel configurations, the two types differ in the driving flanges and wheel studs. Wire wheel driving flanges are splined and handed (right-hand and left-hand), while steel wheel flanges use a straight five-stud pattern. Steel wheel axles are available on a customer's own unit reconditioned basis for 3.071:1, on a standard exchange for 3.307:1, and on a one-for-one exchange for 3.7:1. Wire wheel axles follow the same availability pattern.
Individual crown wheel and pinion sets, differential cages, propshaft flanges, driving flanges, wheel studs, and wheel nuts are all available for those rebuilding an existing axle.
Quaife Limited Slip Differential
A Quaife limited slip differential (LSD) is available as a performance upgrade. With a standard open differential, if one wheel loses grip the other loses drive immediately, a limitation that is particularly noticeable on wet roads, during spirited cornering, and when accelerating hard out of slow corners. The Quaife LSD compensates by transferring torque proportionally to both wheels, providing excellent traction when accelerating and improved stability when cornering. This is one of the most transformative handling upgrades available for the MGC.
Wire Wheel Conversion Kit
A wire wheel conversion kit allows MGCs originally fitted with steel disc wheels to be converted to wire wheels. The kit includes specially adapted rear splined driving flanges that compensate for the greater width of the steel wheel axle, creating the correct wheel arch clearance for wire wheel fitment.