overdrive in a car

  • Thread starter Thread starter Aneuploidy
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Aneuploidy

does turning overdrive on and off all the time make any difference to the
car's performance. ?? i have a friend who believe's it does and he does
it frequently. he drives a holden apollo 1989 and i would think it would
cause a problem somwhere sooner than later and there woudnt be a point in
his car. does it have any negitive effect on the engine itself ?
comments appreciated.
 
Does the car have a standard or an automatic transmission?

Either way, switching it on and off frequently doesn't seem to make a
lot of sense, unless maybe you drive in an area where you're constantly
changing from very hilly terrain to flat. It could cause the OD relay
or solenoid to fail early, leaving you without OD until it is repaired.

Driving mostly with it off causes the engine to run faster for the same
driving speed. Overall this raises your fuel consumption and - if all
other things remain equal, which they never do - would increase the rate
of engine wear due to more engine revolutions per distance travelled.
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Aneuploidy said:
does turning overdrive on and off all the time make any difference to the
car's performance. ?? i have a friend who believe's it does and he does
it frequently. he drives a holden apollo 1989 and i would think it would
cause a problem somwhere sooner than later and there woudnt be a point in
his car. does it have any negitive effect on the engine itself ?
comments appreciated.
Click to expand...


If it's an automatic then the only reason to turn the OD off is towing a
trailer or going up a steep incline when the tranny is shifting back and
forth a lot, otherwise the OD will only engage when cruising anyway so
turning it off will only increase fuel consumption, won't hurt anything,
just doesn't help.
 
Automatics should be left in OD unless desending a very steep hill, then put
it into drive 3, or if the tranny can't make up its own mind of what gear it
should be in... There is no performance difference.... Of course if you need
to have a kickdown from 4 to 3 instead of being right in 3rd gear then yea,
a split second.

As for manuals... it's basically a matter of how high you want your engine
to rev when you could be running 4th, or you could be running 5th.
Personally I use 5th only on the express highways, unless I am on a standard
highway (80kph limit road) that is nice and flat and I can drive a constant
speed.... If you have one of those Volvo trannys with the button you're out
of luck for my suggestions, never have played with one... Seems kinda
annoying tho.
 
Rob Guenther said:
Automatics should be left in OD unless desending a very steep hill, then put
it into drive 3, or if the tranny can't make up its own mind of what gear it
should be in... There is no performance difference.... Of course if you need
to have a kickdown from 4 to 3 instead of being right in 3rd gear then yea,
a split second.

As for manuals... it's basically a matter of how high you want your engine
to rev when you could be running 4th, or you could be running 5th.
Personally I use 5th only on the express highways, unless I am on a standard
highway (80kph limit road) that is nice and flat and I can drive a constant
speed.... If you have one of those Volvo trannys with the button you're out
of luck for my suggestions, never have played with one... Seems kinda
annoying tho.
Click to expand...

There's nothing special about the pushbutton overdrive, it works just like
any other 5th gear except you push the button instead of move the gearshift.
It's kinda nice actually since you can downshift to 4th without touching the
clutch if you want.
 
Hmm... but you need the clutch to bring it up tho?

Maybe that would be better then going for fifth gear, which always seems to
need a really deliberate motion to engage in the standard tranny cars I have
driven.
 
Rob Guenther said:
Hmm... but you need the clutch to bring it up tho?

Maybe that would be better then going for fifth gear, which always seems to
need a really deliberate motion to engage in the standard tranny cars I have
driven.
Click to expand...

You don't *need* to clutch to do either, but a lot of them engage pretty
roughly if you don't, I usually clutch for both engage and disengage,
there's been arguments both ways on this but it seems logical that taking
the load off it before shifting would reduce slippage and wear.
Disengagement without clutching is quite smooth though.
 
Cool...

I asked my dad about the overdrive button, but he said his 240 and two 140's
didn't have it, they were 4 speed (he thinks the 4th gear was an OD, but
isn't 100% sure, is this possible, or is it a direct ratio). He said our
740's had a button on the side to disengage overdrive, and a large button on
top to press down to shift into gears.
 
Rob Guenther said:
Cool...

I asked my dad about the overdrive button, but he said his 240 and two 140's
didn't have it, they were 4 speed (he thinks the 4th gear was an OD, but
isn't 100% sure, is this possible, or is it a direct ratio). He said our
740's had a button on the side to disengage overdrive, and a large button on
top to press down to shift into gears.
"James Sweet" <[email protected]> wrote in message
Click to expand...


4 speed would be the M45 transmission, or maybe that was M40, I forget,
either way 4th gear is the same as on an M46, it's 1:1.

The 740 had an AW-71, the button closes a solenoid valve that locks out 4th
gear. You don't often have to use that.
 
I think we used it for towing, that's about it... Use it about the same as
we use Drive-3 now.
 
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