The Austin Healey BN1 3-speed complete gear set is a comprehensive replacement for worn or damaged transmission components. Designed specifically for the early Healey 100 models produced between 1953 and 1955, this kit restores the correct factory gear ratios and ensures smooth, reliable operation of the BN1 gearbox.
This gear set is engineered for the Austin Healey 100 BN1, which used the unique 3-speed gearbox paired with overdrive. Later BN2 and subsequent Big Healey models adopted a 4-speed unit and require different parts. Owners should confirm the gearbox type before ordering to avoid compatibility issues.
The set provides all major gears required to overhaul the BN1 3-speed transmission. Each gear is precision manufactured to OE specification, offering reliable engagement and correct meshing with existing shafts and synchroniser hubs.
The BN1 gearbox was derived from Austin’s 4-speed column-change saloon gearbox used in the A90 family (and related A70 units). For the Healey 100, it was reworked into a 3-speed layout, with first gear blanked off and overdrive added on 2nd and top. This design gave the car long-legged cruising ability while keeping the gearbox compact, but it also meant that wear on 2nd gear and the layshaft cluster is common after decades of use. Replacing the full set ensures balanced wear across all gears and prolongs the life of the transmission once rebuilt.
The complete BN1 gear set (GBT200) is supplied with new synchro rings already fitted, so no additional synchros are required. During installation it is advisable to check supporting components, as worn bearings or a tired layshaft can shorten the life of a rebuild. The 1st Motion Shaft Bearing, Mainshaft Bearing, and Layshaft are all common wear points in the BN1 gearbox. Replacing these items alongside the new gear set helps ensure smooth running and long-term reliability once the gearbox is back in service.
This complete gear set fits the Austin Healey 100 BN1 (1953–1955) equipped with the original 3-speed gearbox. It is not suitable for BN2 or later models, which used a 4-speed gearbox.
Yes. The kit contains the main gears required for a full rebuild of the BN1 3-speed gearbox. Other components such as bearings, layshafts, and synchroniser parts are available separately and should be inspected during rebuild.
Yes. The gear set is designed to operate with the factory overdrive unit fitted to BN1 models. The overdrive components themselves are separate and unaffected by the gear replacement.
The BN1 3-speed gearbox was fitted to Austin Healey 100s up to chassis number 221535. From BN2 onwards, cars used a 4-speed gearbox. Checking the car’s chassis number and counting forward gear positions will confirm which unit is installed.
The complete BN1 gear set (GBT200) is supplied with new synchro rings already fitted, so additional synchros are not required. However, it is strongly recommended to inspect and, if necessary, replace supporting components such as the 1st Motion Shaft Bearing, Mainshaft Bearing, and Layshaft. These are common wear points in the BN1 gearbox, and replacing them at the same time ensures the best long-term reliability once rebuilt.
30% STRONGER WITH SYNCHRO RINGS FITTED
