<VladicRavich@gmail.com> schrieb im Newsbeitrag
news:1179766696.337755.317270@y2g2000prf.googlegro ups.com...

>I just bought a 1989 Volvo 740 GL and it has that button for the
> overdrive. What does it do?

It is an extra little gearbox with one gear and a little clutch outside the 4
gears-gearbox. It can be engaged only when you are in forth gear. The 4 gears
are shifted mechanically, the overdrive is controlled by a solenoid and oil
pressure when you press the button in 4th gear. It is practically a 5th gear.

>and when should I use it?

You use it like a 5th gear as soon as you have reached the rpms when you would
change gear with a 5 gears manual gear box. Be sure to use the clutch before
pressing the button. When you want to shift back to gear 4, press clutch again
and press button again. When you are in gears 1, 2, 3 the overdrive can not be
engaged. The overdrive is also controled by a relay near the fuses.

> answer. I'm sure whatever it is, it's only half as endearing as the
> hand cranked sunroof.

did you mean enduring? I have one with 376.000 km. The only thing I have
replaced is the relay some time ago.

http://en.wikipedia.org/wiki/Overdrive_%28mechanics%29 gives more info.

Viktor