An OD uses a planetary gear set. Look at the gears in Richard Gosling's
link.
In the center is a single gear called the sun. Around that are several
gears called planets, and out side that is the ring or annulus gear.
If you hold any two of these gears together, the entire unit rotates as one
solid piece. so lock the sun to the planets, sun to the ring, or planets to
the ring, and you have a solid unit. This is gears 1-4, +reverse
If on the other hand you hold one gear stationary, supply power to one of
the other two, you get a speed changed out of the third. OD.
In your OD is a thing called a cone clutch. When no oil pressure is
applied, springs force the cone clutch to where it locks two of the
components together. (Sun and planets I think, but I would have to look at
a diagram to be sure.)
When you hit the switch, the solenoid allows oil under pressure to go to the
apply pistons which shove the cone clutch the other way, and it brakes one
component. The trans output shaft supplies power one of the remaining two
gears, and a speed change is had out of the third.
Again, I am not sure without a diagram, but I think the ring is braked (held
stationary) and power goes to the planets, and the output is from the sun.
BTW the oil pressure comes from a very simple eccentric pump on the output
shaft of the trans.
I used to rebuild Laycocks on Volvos, very simple, very rugged design.
Hope this helps,
Rick
On 9/21/07, Malcolm Jeffcock <msjeffcock@eastlink.ca> wrote:
>
> My B has overdrive and thankfully it is working fine. My question though
> may be simple but how does it actually work? I appreciate it is an
> "electric" overdrive but that electrical component must somehow be
> transferred to a mechanical advantage. I pondered this while driving back
> fro Halifax yesterday...the places you your mind goes when driving in the
> sun with the top down!
>
>
>
>Malcolm
> _______________________________________________
> richard.ewald@gmail.com
>
> Edit your replies
>
> Mgs@autox.team.net
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