gearbox & overdrive More sub catagories: Gearbox gearbox mountings Overdrive

New products 3,40 EUR incl. 19 % tax excl. screw 1 1/8" - 5/16" UNF 0,95 EUR incl. 19 % tax excl. screw 3/4" - 5/16" UNF 0,80 EUR incl. 19 % tax excl. nut - half 3/8" UNF half x 3/8" UNF, spanner size: 9/16" 0,75 EUR incl. 19 % tax excl.

A single dry-plate Borg & Beck clutch was fitted to all these cars, but unlike the 100 clutch actuation was now hydraulic, with a shared reservoir for the brake and clutch fluids (except some late export models). The pendant clutch pedal directly activated the master cylinder fitted on the pedal box, and the clutch operating or slave cylinder was found on the right-hand side below the bell housing. The 100-Six models had a 9in clutch, while on the 3000 models this was increased to 10in. In May 1963, from engine number 29F/4898 on the Mark II Convertible, a new 91/2in diaphragm spring type clutch was introduced. The final change occurred on the Mark III from engine number 29K/4108 in October 1964 when the clutch was reduced in size to 9in.

The standard BMC four-speed gearbox found on the BN2 version of the 100 was carried over on the 100-Six, with the same internal gearbox ratios. The gearlever was silver, the knob a black ball with an engraved white pattern. The overdrive ratio was also unchanged. As previously indicated there were two different rear axle ratios depending on whether or not overdrive was fitted, and so we obtain the following table of 100-Six gear ratios:

On the 3000 Mark I model from the beginning of production, the internal gearbox ratios were revised, and in conjunction with the altered rear axle ratios produced the following sets of ratios:

It will be noted that these revisions affected first, second and reverse gears, and were relatively minor. Apart from other smaller gearbox changes listed in 'production Changes', the next important change occured in November 1961 when the 3000 Mark II models were given a new gearbox design with top rather than side selectors, and it became possible to have a true centre gearchange with a short, vertical lever rather than the former side gearchange with the cranked lever. This modification took place from engine number 29E/2246, chassis numbers BT7/15881 and BN7/16039. The ratios were not changed, however.

The final revised set of gear ratios was introduced on the Mark III model from commencement in October 1963; otherwise this model took over the existing gearbox without major change. On the Mark III models the following ratios were found: