The MGB GT V8 was fitted with the tube-type rear axle, a Salisbury-style design where the axle case is a single tube with the differential carrier mounted at its centre. The tube axle replaced the earlier banjo-style axle on the MGB range from 1967 production and is the type fitted throughout the V8's production. The axle case carries the half-shafts internally and supports the hub bearings at each end, with the differential housing accessible by removing the rear cover.
Final Drive
The factory final drive ratio for the MGB GT V8 is 3.071:1, achieved with a 14-tooth pinion driving a 43-tooth crown wheel. This ratio was chosen to give the V8 long-legged cruising at British motorway speeds with the overdrive engaged, taking advantage of the V8's substantial torque to accept a tall final drive without losing acceleration. The 3.071:1 ratio is unique to the V8 within the MGB range and is not interchangeable with the four-cylinder MGB ratios.
Crown Wheel and Pinion
Replacement crown wheel and pinion sets are available, supplied as matched pairs as the two gears are lapped together at manufacture. Setting up a new crown wheel and pinion requires specialist measurement of pinion depth and backlash, this is precision differential work that should be done by an experienced gearbox specialist.
Differential Bearings and Seals
The differential carrier runs on tapered roller bearings at each side. The pinion shaft runs on tapered roller bearings at each end, with an oil seal at the front where the pinion flange exits the axle case. Bearings and seals are wear items typically renewed during a differential rebuild.
Half-Shafts and Hub Bearings
Half-shafts transmit drive from the differential to the road wheels, splined to the differential side gears at the inner end and flanged for the rear hub at the outer end. Hub bearings carry the half-shafts at each axle end and are renewed during axle work or where bearing roughness develops.
MGOC Spares
MGOC Spares supplies tube-type rear axle components, crown wheel and pinion sets, differential bearings, half-shafts, hub bearings and seals for the MGB GT V8.