There are more variables than just efficiency when designing a gearbox.
With modern oils and machining techniques the difference in efficiency
between direct and indirect ratios is not that great.
A gearbox is only as strong as its smallest drive gear. In order to get
the spread of ratios demanded by today's cars and package the gearbox in as
small of an area as possible, overdrive ratios are necessary. You can't
get enough spread between one to one and first gear in a six speed that
handles 400 horsepower without it becoming the size of a small horse. All
of the gears would get bigger so synchros would have to work harder, more
inertia loss, poorer shift quality, etc.
Regards,
Bill Eastman
61 MGA
|