(O)verdrive or just plain Drive?

[sixf00t4]

what is the difference in cars?

what should i be driving in, in what conditions/terrain?

call me lame for this next one, but i hate cars, and am using my brother in law's now to get to some jobs. when should i drop to 1/2/3 gears?

[skuz]

According to my father's habit, you should always have the overdrive on, except when you have a trailer.

Me I don't know, haven't had an automatic myself.

[Redwolf]

Overdrive is like a higher gear that the gear the car is currently in. It lets the car run faster at lower RPMs, but with less power. Turning off overdrive is useful for going over unpaved roads or going 'off-road'. For me, 90% of the time overdrive stays on.

If it's an automatic, you'll never have to drop gears, the car will do it for you. And what Skuz said about overdrive. The only other time I would shut OD off is if you're in the city and you get going fast enough that the slow down/speed up causes the car to shift between OD and D a lot. Otherwise, just let them do what they're made to do.

If it's a stick, you can generally apply the same principle for overdrive. Drop gears when you feel the car hasn't got enough power to get up an incline or accelerate. If you're moving and going up a hill, you generally want the RPM range to be above 3/8s of what it's capable of (in my experience). In my truck this does not apply because 3/8s doesn't have enough power to motor up a lot of inclines. It's pretty vehicle dependant, but with a little bit of experience, you'll catch on (and pretty quickly if you keep bogging the motor down ).

[Gomer]

AT's have 3 speeds usually (1,2,D) or 4 (1,2,D,OD). OD is just a fourth gear that is most efficient.

I drive almost expressly in OD. You car will not accelerate fast in OD as it would in D (say speeding up from 50-65). However, most cars readily downshift from OD to D with ease for the purposes of merging. The only time you may not want to use OD is in city driving where you feel it downshifting alot. However, I drive pretty hard in OD everywhere and it works fine for me. Computers handle it all these days. OD usually is shifted into over 50.

Below 50, driving in OD also affects the shift timing so that it shifts earlier in all gears. This will result in a slight acceleration hit, but will increase MPG.

Look at it this way. If you are driving 65 MPH in D you will be turning more RPM then the same speed in OD. And more RPM ='s more fuel gobbled up.

[OuTpaTienT]

Overdrive is like a 5th gear in a 5 speed. It really only needs to be on when on the freeway or cruising at highway speeds. For the most part you can turn it off while city driving. But it's probably not the end of the world if you just leave it on.

[OuTpaTienT]

Originally posted by Gomer

Below 50, driving in OD also affects the shift timing so that it shifts earlier in all gears. This will result in a slight acceleration hit, but will increase MPG.

That I did not know.

[Gomer]

OD also will affect torque converter lockup in some cars I believe.

The torque converter is what allows your car to idle in drive and to shift without a clutch. Imagine a fan blowing air into a fan that is turned off. The off fan will spin from the air going by. Similar thing in your car except it is tranny fluid not air which results in a much greater couple. However, some energy is lost in this process.

Torque converter lockup occurs at cruising speed in OD. The two "fans" are mechanically coupled together via a solenoid which negates the energy loss typically incured by the fluid medium.

[Gomer]

http://cartalk.cars.com/Columns/Arch...tember/17.html

http://cartalk.cars.com/Columns/Arch...97/May/20.html

http://cartalk.cars.com/Columns/Arch...tember/01.html

[sixf00t4]

it is an automatic. i do drive only in (O)verdrive (i like the way the put the O in paranthesi) i do a little city driving though, perhaps i should go in drive. if i can remember to break my habit...

You car will not accelerate fast in OD as it would in D (say speeding up from 50-65). However, most cars readily downshift from OD to D with ease for the purposes of merging.

you have me thinking Gomer...the car will jerk REALLY bad when i am making (what seems to be only left??) turns. like i will come to a stop light intersection, let my foot off the gas, and when i go to accellerate through the turn, it just flips out on me. perhaps that is an (O)ver drive issue? i am not jamming on the gas or anything, any pressure applied to the pedal at all and you can hear the engine going but the gears not catching.