The tube axle was introduced on GT models from 1965 and became the standard fitment on all MGB roadsters from approximately 1967, remaining in production through to 1980. Unlike the earlier banjo axle, the tube axle is a one-piece casing without a bolt-on differential centre, making internal work more involved. For most owners, a complete reconditioned exchange axle is the most practical route.
Reconditioned Axle Assemblies
Complete reconditioned tube axles are available in four variants, steel wheel or wire wheel, and pre or post September 1976, on a one-for-one exchange basis. All reconditioned axles are supplied without brakes or hub/flange assemblies, which must be transferred from or sourced separately. An important note for automatic transmission cars: the automatic gearbox MGB used a 3.7:1 ratio axle from chassis GHN4/GHD4-158231 onwards. Before that chassis number, automatics shared the standard 3.909:1 ratio.
This affects crown wheel and pinion selection if rebuilding an automatic car’s axle.
Differential Rebuild
For owners undertaking a differential rebuild, the internal components follow the same layout as the banjo axle differential but use tube-axle-specific parts throughout. The differential carrier bearings are shimmed using distance collars available in incremental steps from 0.115” to 0.149” to achieve the correct backlash setting. Pinion depth is set using thrust washers available from 0.208” to 0.222”.
Hubs & Half Shafts
Hub assemblies differ between steel and wire wheel cars. The steel wheel drive flange and wire wheel splined hubs (RH, LH) are 8 TPI, unlike the early banjo axle cars, there are no 12 TPI tube axle hubs. Half shafts also differ between steel wheel and wire wheel cars. The Axle Clonk Cure kit addresses a common issue on tube axle cars where wear in the axle strap mounting allows the axle to move under load, producing an audible clonk on acceleration and deceleration.
This is a frequently overlooked wear point and is worth inspecting before attributing the noise to differential or propshaft issues.