Well I recently got a 95 mustang gt. It has always had overdrive off and I was wondering if I should have it off because I usually only do city driving so I stop and go a lot. So i'm wondering if its better to just keep it on all the time to put less stress on the motor, or if I should just take it off so I can accelerate faster and not have to give it as much gas. What are the conditions as to when it should be off and when it should be on? I'm not quite sure because I'm still trying to learn how gears work and the logic behind it. Any response would be appreciated as I'm trying to learn about this car
Overdrive is any gear less than 1.00. This gear is a lot less powerful but saves fuel. Since you have an AOD, you have a 4 speed transmission: 3 regular gears and an overdrive.
Driving around with overdrive off is ok for city I guess. It's just going to limit you to 3rd gear which means that you will be able to drive faster without having to floor it all the time (obviously when you are at a higher RPM, you will have more power available). If you are on the freeway, you need to turn overdrive on. You will waste a lot of gas and probably do damage to your engine from running a higher rpm for that long.
The only times I would really turn off OD is if you are in the city or need to have power available without flooring it. A good example would be pulling hills. If you drop it into 3rd going up a hill, you won't have to floor it and waste gas to get up it. Of course, if you have a V8 motor you really shouldn't have to worry about available power.
Unfortunately, I can't explain in specifics how the overdrive gear works. I think it has something to do with the engine not having to work as hard in order to keep the car moving.
Thanks a lot, that pretty much explained things. So I just read my message over again and I lied, I meant I have always had overdrive on. So recently i've been noticing when I'm at a red light for example, and it turns green, it takes me longer to accelerate then other cars, unless i really floor it. So i'm thinking to myself, there is no way that accord has more power then me, there is something going on here. It makes sense now though, thanks.
if my moms rav4 i lead it on overdrive all the time, because it never really is in overdrive unless i get on the freeway or something.. If ur in overdrive and you slow down, it will shift out when you take off..
You can leave it in overdrive, because in town you aren't going to get going fast enough to have the car shift into overdrive and if you are you should leave it in drive so you can outrun the cops that will be all over you for driving too fast.
Having overdrive on does not affect your acceleration/power in lower gears. "Turning it on" tells the transmission that it's ok to shift into 4th gear when certain conditions are met (i.e. mph and acceleration rate, usually way too early in my opinion - especially with later model cars). Otherwise, it will stay in 3rd.
I only use overdrive when I know that I'm going to be driving at or above 35 mph for an extended period of time. I figure why make the transmission shift gears when it's just going to downshift a second or two later? If you were driving a stick, you wouldn't always shift into 5th when you reached 40 mph under normal acceleration, would you? It just seems to me that it saves some wear and tear on the trans.
k.. so I should turn it off when I am in town.. sometimes I get it up to 40.. then I have to stop.. then I go again and finally get it up to 35 - 40.. and have to stop again, and I can feel it switching. I've always had it on so I dunno if its time to start turning it off in town or what..
I guess it basically boils down to personal preference. The only time I put it in overdrive is when I don't anticipate stopping for at least the next 3-5 minutes or so. I mean, I don't sit there with a stopwatch in my hand - pretty soon it just became habitual. I know the roads I drive on, and I know which lights I always get caught by
I've switched it off when I'm going about 30-40 MPH and need to pass an idiot that's going 20 without flooring it. It takes just a tap on the accelerator and she's in my rearview mirror. Then I switch back to O/D.
if you read the owners manual, you will find that ford recomends that for city and mountainous or hilly driving, it is best to turn off the o/d as it will over stess the system and bring about early trans failure. o/d is best used when you are going 40mph and above for extended periods of time.
Proper time to use overdrive.. confused. 
in my rearview mirror. Then I switch back to O/D.
