🚀 go-pugleaf

Can someone explain the relative merits of having a 5 speed transmission
vs. having a 4 speed with an overdrive box tacked on?  Is the end
result the same (i.e. 4'th in both schemes is a 1:1 ratio between crankshaft
speed and propeller shaft speed; overdrive/5'th being 1:>1)?

It would seem to me that, this being the case, a 5 speed transmission
would always be superior to a 4 with overdrive - less parts, complexity,
etc.  Is overdrive just a marketing ploy?  A recent poster mentioned that
Volvo supplies (as an option) an overdrive for its transmissions.  Volvo
has addressed the needs of the highway cruisers this way since at least
1960.  As far as I know, their transmissions (the M40, M400, M45) have
always been 4 speeds - you can get an overdrive box for any of them
however.  Why not simply make a 4 speed and a true 5 speed box?  The
cost has got to be lower to slap another gear (and make the box a bit
bigger) into the transmission instead of adding what amounts to a
whole 'nother (2 speed) transmission onto the output of the first.

Note that I know that 5  speed is sometimes called overdrive even on
true 5 speed gearboxes.  By overdrive I mean an extra electro-hydraulic
box attached to the output of the main gearbox.

-- 
    Gregory R. Travis
    Institute for Social Research - Indiana University - Bloomington, In
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