History of the 100:

The 100 is the first real Big Healey despite its 4 cylinders.

The mechanical base: Austin A90 transmission engine, standard BMC gearbox for the BN1.

The 100 was built in two variants:

the BN1 series, with three speeds, was built in 10,688 units and the BN2 series with four speeds, built in 4,600 units.

On the BN1, the too brutal first gear was locked but the box retains the final length.