<P> Where large numbers of gear ratios, six or more, are to be provided then these will require a third or more gear clusters on the layshaft . To maintain the proportions of the overall gearbox as more compact, rather than becoming long and thin, these gearboxes may use twin layshafts . This requires an additional driven gear for each layshaft, but the mechanism is otherwise very similar . The use of multiple layshafts also developed into the multiple clutch gearbox, used for some buses, where each ratio has its own layshaft and separate plate or hydraulic clutches, rather than dog clutches, are used to select between them . </P> <P> Where a power take - off is required, usually for industrial vehicles to drive winches, hydraulic pumps etc., this is often driven from one end of the layshaft, as this is more accessible shaft than the main shafts, already in use by the drivetrain . </P> <P> Some gearboxes do not use a layshaft, but rely on indirect gears throughout . </P> <P> All - indirect were used for some very early cars, before the advantages of the direct - drive top gear were recognised . They contain no dog clutches; at the time, gear changing was still carried out by sliding the gears in and out of mesh . Once the dog clutch came into use, the further advantage of a direct - drive top gear was immediately recognised . </P>

What connects the gears to the drive shaft in a manual transmission