Overdrive

[Bodin]

On my 91 Ford F-150 I have an overdrive button and when you start the vehicle the overdrive is on. You have to push the button to turn it off.  

My question is should I have the overdrive on when I am on the highway and off when I am in the city?

[mrthompson]

Doesn't really matter.  Your transmission won't shift into Overdrive unless you are going at the right speed, and under the proper conditions.  

I leave the tranny in my Jeep in Overdrive UNLESS I am towing, or if I am driving on streets/backroads at speeds less than 70 km/hr.  That's my personal rule of thumb.

[Bodin]

would you get better gas milage in overdrive or no overdrive?

[brian]

In.

Overdrive is nothing more than the top gear in the transmission (usually 4th or 5th).  The button just tells the transmission never to shift into 4th (or 5th).  You really don't ever need to turn it off unless towing or going up hilly areas, or optionally in city driving, but even that is usually unnecessary since you don't damage anything by enabling overdrive, and most cars do not have an overdrive lockout button anyway.

[Roadrunner]

If you do a lot of trailer towing, (doesn't matter the size if loaded all the time) and drive in hilly or intown stop and go traffic, the tranny will heat up from the constant shifting in and out of OD. If your speed is up to the shifting rpm that is. The heat is what causes tranny damage, accumulatively.

[barrie1]

It actually changes the gear ratio's that your tranny shifts at with the button turned on. Read what the owners manuel says about this design keep the Fluid and filter clean and drive as the book says. It may save you a bunch of money some day.

[maritime_storm]

Leave it in overdrive on the highway, off in the city. You'll save the transmission by doing this, it prevent the transmission from constantly shifting in and out of overdrive, that why Ford offered this option. The newer models won't go into overdrive until higher speeds.

[Bodin]

thanks for clarifying this for me

[Sterling]

Wrong, wrong, wrong Barrie1 and Maritime_storm.

The overdrive button works exactly like Brian described it above. All it does it prevent the transmission from shifting into 4th gear. It changes nothing to do with gear ratios and it saves nothing by shutting it off in the city. Transmissions are made to shift gears when necessary. The transmission will not wear out sooner if you let it shift gears. By shutting off overdrive in the city all you are doing is ruining your fuel economy.

[Shnak]

That's not how it worked in my CR-V Sterling. When overdrive was off, the transmission would remain in gears longer while accelerating, and always waited until revs would get a lot higher before shifting.

In my CR-V, I used to only turn the overdrive off when I wanted my vehicle to feel "sporty" and make it rev more.

[Sterling]

The original post is regarding a '91 F-150. That's how they work.

[Shnak]

ok maybe you meant to explain how the overdrive button worked in his '91 F150, but it really seemed like you were saying that every single overdrive function worked like you described it, which is clearly not the case.

[Sterling]

No, all I said was that 2 other posters advice to the thread starter was incorrect.

[barrie1]

Sorry Sterling I stand by what I wrote on the gear ratio's being changed on shifting. Why is there a switch in the 1st place? What was the purpose of it. The early GM's went south when you drove them in 4th all of the time in the city and so did a lot of the others. They are probably much more advanced now but the early 4spds ran that way. Read the owners manuel as see what it says. Ford and Chrysler had the same problems as GM on the 4th gear issue.

[Sterling]

You are incorrect about how that overdrive button operates. The reason it exists is to prevent excessive shifting between 3rd and 4th gear while towing a trailer or going up steep hills. Without the lockout button the truck would accelerate in 3rd, shift to 4th, not have enough steam to maintain speed, downshift to 3rd, accelerate, shift to 4th, run out of steam, downshift to 3rd, etc., etc. By pressing the button and locking out 4th gear, the driver will prevent that excessive shifting between 3rd and 4th. This is only an issue if pulling a heavy load although the same thing may happen with an unloaded truck if going up a long, steep grade.

Sorry Barrie, but I consulted with the transmission tech at the Ford dealership I work at before posting this. I have a lot full of trucks to check owners manuals. I will post what they say if you want.

[maritime_storm]

Sterling you repeated exactly what I posted up top, but it wasn't just when towing that it would do this, they tended to upshift at light throttle around 60kph into overdrive. Then as you described they would hunt back and forth. And as Barrie said they would eventually destroy the bands on the 4th gear especially and usually the 3rd gear as well. Most newer transmissions are computer controlled and programmed not to hunt back and forth thus saving the tranny{in theory}.

[Shnak]

I guess Honda's overdrive technology is more advanded then Ford's then. In my CR-V, it clearly shifted at different times, waiting for higher rpms before shifting, and for every gear, not just 3rd and 4th like you explain Sterling. I always believed that's how it worked for every car.

[Driver]

My old 03 Corolla behaves like shnak's old CRV when overdrive is OFF i.e. shifting at diff times depending on RPM range.

My current Subie however behaves differently as it has no overdrive (visible) switch. I'm assuming it's "3" that equates to overdrive OFF. Also, according to my manual, it says in "2" starts on 2nd and holds on to 2nd (no shifting)

I'm sorta confused by this subie transmission

[multipath]

I think it depends on how sophisticated the transmission is.  I find my Protege sticking to 3rd when hill-climbing where most older automatics would be hunting between 3rd and 4th.  I always drive it with O/D button on, and let the car decide, unless there is a specific reason I want to lock out 4th.

I recently drove an early '90s Astro when helping a friend move a short distance.  I found at city speeds (relatively light load of cargo), the vehicle was really labouring in 4th, almost sounded like it wanted to stall, so on that vehicle, I had to lock out 4th.

[barrie1]

Sterling the older Fords had the switch to do that with for the reason you describe but not all of the manufacturers did. I have worked out of Vehicle Distribution of a large Co in Canada and have seen this problem like I described it. They are 2 slightly different designs for the vintage. A friend of mine just damaged his 2002 Sonoma's overdrive by leaving it in 4th too much and driving too slow on the highway with it. This is a service truck for his business and it is the 3rd one he has done this too. He keeps forgetting to leave it in 3rd in the city.