Use overdrive or not?

[maxddr19]

Should I keep the overdrive on in my car? I've heard that it helps you get better gas mileage and you're not supposed to have it on in rough terrains or hills, which I don't come close to any day driving.

 

[CountryDSM]

http://www.dsmtuners.com/forums/automatic-tranny/335378-should-i-keep-my-overdrive-switch-off.html

 

[DSM1G90]

I'd leave the OD on at all times - let the tranny do what it's supposed to do.

Only good time to leave OD off is during the winter in town driving when you can use the motor for engine braking so you can control yourself on slick streets.

 

[Iodes]

In my previous '95 NT I didn't use overdrive unless I was going above 40 mph. It should be off during stop-and-go through a city and on when you're driving on a highway at a constant speed. I also turned it off when going uphill so my car had the power of higher rpm's. Now I have a turbo model and leave overdrive on unless I'm idling in a parking lot, climbing a steep hill or hitting every red stoplight, which is not often.

Based on the above thread link, I would say your personal driving routines determine how you should use overdrive. At the very least it must be on when you are driving and maintaining a constant speed for an extended period of time.

 

[clipto]

I always leave my overdrive on so I dont have to keep pushing it when driving around. I do turn it off when i am racing because sometimes it shifts into 4th gear when i dont want it to.

 

[DSM1G90]

Funny thing about OD is that it's really not OD, but just an extra gear to reduce RPM's and better gas mileage. The button on the shifter makes it available to get out of OD when needed.

Little background to share: All transmission gears are each made to reach a certain torque point at a given RPM of the motor -from 1st to the final gear with the final gear achieving a 2600 rpm at 60mph - the ideal final gear ratio range for motor efficency.

Vehicles of a good two generations ago (and now with 6speed manuals and 6 and up to 8 speed automatics) that had an OD gear was just that..an OD gear which allowed the motor to rotate slower at the 60mph road speed.

Our DSM trannies-in both manual and automatic, does the 2600rpm/60mph operation procedure. Thus, what we REALLY have, in automatic form, is a 3speed with an OD transmission.

Thus, you go out of OD, you're running the tranny in 3rd gear, which will wind the motor up to almost 3200 RPM at 60mph, killing MPG and extra wear on the tranny.

I'd stay put in OD just to save on your pocketbook.

 

[NHerron]

Manual 2G DSM's sit at 3200rpm @ 70MPH.

I'm not a trans specialist here but would venture to say every engine has it's specific efficiency range, lower RPM is not always going to save gas. Such as being in final gear going 20MPH with the throttle down.

 

[Diamond Star Werks]

Funny thing about OD is that it's really not OD, but just an extra gear to reduce RPM's and better gas mileage. The button on the shifter makes it available to get out of OD when needed.

Little background to share: All transmission gears are each made to reach a certain torque point at a given RPM of the motor -from 1st to the final gear with the final gear achieving a 2600 rpm at 60mph - the ideal final gear ratio range for motor efficency.

Vehicles of a good two generations ago (and now with 6speed manuals and 6 and up to 8 speed automatics) that had an OD gear was just that..an OD gear which allowed the motor to rotate slower at the 60mph road speed.

Our DSM trannies-in both manual and automatic, does the 2600rpm/60mph operation procedure. Thus, what we REALLY have, in automatic form, is a 3speed with an OD transmission.

Thus, you go out of OD, you're running the tranny in 3rd gear, which will wind the motor up to almost 3200 RPM at 60mph, killing MPG and extra wear on the tranny.

I'd stay put in OD just to save on your pocketbook.

All transmissions are not geared to reach 60mph at 2600. I can assure you that. Dsm auto, manual are diff, dsm n/t I believe is different. Hondas are diff. Etc. every motor is different and reaches peak torque diff and gearing is setup for that engine.
Saying "all transmissions" is bad info.

 

[Leonthefaded]

This is all very interesting. So OD should be left on during Highway or driving over 40 MPH? and City driving or speeds under 40 MPH OD can safely be off without worry about extra wear on your auto transmission? I'm just trying to paint a clear picture for myself.

 

[maxddr19]

Well I have an automatic.

 

[NHerron]

In my previous '95 NT I didn't use overdrive unless I was going above 40 mph. It should be off during stop-and-go through a city and on when you're driving on a highway at a constant speed. I also turned it off when going uphill so my car had the power of higher rpm's. Now I have a turbo model and leave overdrive on unless I'm idling in a parking lot, climbing a steep hill or hitting every red stoplight, which is not often.

Based on the above thread link, I would say your personal driving routines determine how you should use overdrive. At the very least it must be on when you are driving and maintaining a constant speed for an extended period of time.

Most cars are not programmed to go into overdrive below a certain speed, usually around 45ish. It's pointless to turn it off in city driving in other words.

The car will automatically downshift if load is high enough, such as a hill. Again. pointless to disable, unless the car starts 'gear hunting' (switching back and forth from OD to 3rd)

To the OP; Disable it if you start catching speed on a downhill. However, be very careful if there is rain/snow/ etc on that downhill. The sudden change in the cars' rolling resistance could cause tires to cut loose.
Disable it if your car is heavy and the trans is shifting back and forth from OD to 3rd [gear hunting]

...Unless I'm idling in a parking lot...
Hmm. That's a new one.

 

[DSM1G90]

every motor is different and reaches peak torque diff and gearing is setup for that engine.
Saying "all transmissions" is bad info.

with all the manual cars/trucks that I've driven in my years, all of the tachs (add-on and factory) posted 2600rpm at 60mph in top gear is why I said that - even my Laser posts the same reading on both gauges. If it was then different, I wouldn't have posted this info.

New vehicles built in the last couple of years are definitely void of this info.

 

[1990AWD]

You people are over complicating the hell out of this. All the O/D switch is is keeping from going into 4th gear (which is an overdrive gear meaning less than 1:1 gear ratio). Just like putting the transmission in 1st keeps it in first, 2nd only allows it to go up to 2nd gear, etc.

If you're going fast enough for the transmission to upshift to fourth (O/D) then push the button and allow it to.

 

[1990AWD]

with all the manual cars/trucks that I've driven in my years, all of the tachs (add-on and factory) posted 2600rpm at 60mph in top gear is why I said that - even my Laser posts the same reading on both gauges. If it was then different, I wouldn't have posted this info.

New vehicles built in the last couple of years are definitely void of this info.

Wow, dumber words can't be spoken. My Mom's '00 Cavalier revs at ~2350 rpm at 60 mph, my DSM ~2800, my VR-4 ~2000, our '88 F-150 ~1900-2000. Every car is different, some just happen to fall into coinciding numbers at that given speed.

 

[Phantom DSM]

Wow, dumber words can't be spoken. My Mom's '00 Cavalier revs at ~2350 rpm at 60 mph, my DSM ~2800, my VR-4 ~2000, our '88 F-150 ~1900-2000. Every car is different, some just happen to fall into coinciding numbers at that given speed.

Such a simple question in a thread and everyone has an opinion, yet it turns into a know it all match, come on guys !

Using "dumber" is not going to make your opinion plausible. I do not mean to attack or be rude but, using an insulting word like that is just disrespectful.
Most automatics do hover in the ~~2500 rpm range and many have different stall in torque converters, and geared differently. Results will vary from vehicle to vehicle and how tranny operates. The o/d button switched off will keep you in maximum of 3rd in these cars and to answer your question, will reduce mpg from my experience. Keep it in o/d on highway drives for example and your motor will rev lower and a smoother drive.

 

[DSM1G90]

True, I'm done-didn't mean to start a drama here.

Back on topic: It's all up to the user if the OD is being used or not - some like it for acceleration (like being in 3rd all the time for quicker throttle response) while others want to save fuel and the motor to lope down the streets of town in a casual manner.

 

[Diamond Star Werks]

If your going to be driving in up and down speeds around 40-45mph leave it of as it'll be going in and out anything above that, keep it on.