I have an 87 Volvo DL 240 that I recently bought from a friend. It’s a huge old blue stationwagon and I love the thing.
I’ve been able to figure out just about all the buttons but one. It’s on the gear shifter (the one that allows me to go from park to reverse, etc). There’s a large button on the top of the shifter that I have to press to shift out of park. Then there’s another much smaller button that sits on the left side of the shifter knob. When I press on it, an orange arrow appears on the bottom right hand corner of the dash, sitting among the series of (off) warning lights. The car also seems to rev more, though I’m not sure if that’s the right term or not. I also seem to get kick-ass gas mileage. I say seem, because I have yet to really test it out. It’s more of a casual observation. I know from my manual - a huge book that I got from a car place, that I don’t have turbo, so that’s not it. The book doesn’t even mention the thing. I’ve even asked a few mechanics and they have no clue.
My guess is that it might be some sort of overdrive button, since that option is not on my gear shifter, which includes P R N D 1 2. It might actually be P R N D 2 1, but I’m not sure.
So now I turn to you, dear dopers. What the heck is this thing?
On a couple of the Econo box cars that I was looking at had a little button like that, and it was for the overdrive, but on the dash there was an icon that said something like OD on or off
I think you’re right, it probably is a Overdrive on/off button. Now you just need to figure out if overdrive is in or out.
A semi-WAG but it may disable the torque converter lockup or “overdrive” gear in the automatic transmission. If engine revs increase I’m pretty sure that’s what it is. My truck has a button that basically disables 4th gear in the four speed automatic tranny. IMO it’s only useful to keep the transmission from constantly shifting back and forth from third to fourth when climbing hills or towing.
I’m a bit puzzled though when you say the engine revs more and you get better fuel mileage. did I understand you correctly?
Thanks Q.E.D. After several months of ownership, I finally know what this thing does.
Well, I did say seems to get better fuel mileage. It could just be wishful thinking on my part. I have a one hour commute each way to work five days a week and use up a rediculous amount of gas.
I went to Ask Jeeves and typed in “What is overdrive” and found the following,
(italics mine)
Wouldn’t that mean that if used at higher speeds, overdrive should, in theory at least, give me better fuel mileage?
How would one go about doing this? I am a car novice as you can probably tell. But I am also very willing - and eager - to learn more.
There is an indicator on the bottom left corner of the instrument cluster which will light up when the OD is off. On some DL models, it’s simply an orange arrow, on others, it’s a lighted box which says “OD Off”.
Yes, the purpose of the overdrive is to provide better fuel economy at highway speeds.
I don’t know if the button is the same, but on my mom’s 2000 Volvo, there’s a “W” button on the shifter that, when pressed, lights up an orange arrow on the dashboard. According to the manual, this is the “winter” mode and keeps the transmission in the first three gears - causing higher revving at high speeds. If it’s the same thing, it would give you much worse gas mileage, since you’re not able to use 4th or 5th gear for highway cruising. I think it’s meant to keep the transmission in lower gears at low speeds so you have greater control in situations like driving in snow where traction would be worse.
When I start the car, the little orange arrow is off. It goes on once I press on the button. It’s at this time that all the “extra” stuff starts happening - engine revs, etc.
What are the benefits of disabling overdrive?
I do love the car, scr4. It’s got it’s quirks, for sure, but overall it’s a great car.
Well, my old 1980 Volvo 245 was a four-speed manual, but the concept is the same for an automatic. Okay now, imagine a stick-shift. Generally, any car has four available gears. You always want to start the car from a stop in first gear and generally go no higher than about 15 to 20 MPH in first. Sometimes you can start the car from a stop in second or if you have to turn or otherwise slow down to 15 or 20 MPH you use second. When accelerating, you don’t want to stay in second for much higher than 25 or 30 MPH. Third gear is a slower speed, around-town gear. You can generally use third from about 25 to 45 MPH. Plus, you want to do any major hill-climbing in third. Fourth gear is still usable around town, and I shift into it at generally about 35 to 40 MPH, depending on driving conditions. Now, you can drive a car at highway speed in fourth gear (I used to drive the Volvo on the interstate at 75 MPH in fourth) but you’re wasting gas due to the higher load on the engine.
Now, a lot of cars have a fifth gear. My new Subaru, for example, is a five-speed manual. Fifth is purely for highway travel and brings down the RPMs. You can think of the button-selected overdrive of a Volvo as an electronic shift into fifth. I didn’t use the Volvo’s overdrive a lot, partially because I wasn’t taking many trips out of town with it where I would normally think to put a car into fifth. Also, in the last couple of years, it stopped working properly, due to (I believe) a problem with the four-five soleniod (well, this is about what a mechanic told me.) However, I did notice that it automatically dropped out of overdrive once you got below a certain speed, which I believe was about 50.
The benefits of overdrive are as others said. You drop the RPMs of the engine while maintaining the same speed, thus increasing mileage. I honestly cannot imagine trying to drive with the overdrive button enabled, because I don’t think I could have done it in the old Volvo. If I were you, I would use it for highway travel but not in town. Actually, what this sounds like to me is similar to the automatic in my family’s old Aerostar. There was both a D and a circle D. Circle D indicated overdrive.
The thing everyone’s glossed over is the fact that it’s really an automatic overdrive. It only really kicks in at highway speeds when the engine is under low load. At city speeds, or when the engine is under higher load (such as driving uphill), the OD disengages in order to provide sufficient torque. Turning it off really does disable it, but turing it “on” doesn’t activate it, unless the conditions are present for it to.
Well I’ve decided not to go out after all. A stomach bug seems to have gotten the better of me.
Thanks for all the info, asterion. It has been most helpful. I have driven at lower speeds with the overdrive engaged, and it seems to handle much worse than with the overdrive off. Now when I get to the higher speeds, having overdrive on seems to help with the handling. I can also get it going pretty good without needing to press on the gas peddal quite as much.
Is it safe/better for my engine to switch overdrive on/off when I reach the higher/lower speeds? Or should I wait until I am stopped to do so? My car is older, as stated in the OP, and I don’t want to cause any undue harm to my engine.
That’s odd, Q.E.D., as when I press that button, something definitely happens no matter what speed I’m at. Could it just be that I have an old car and the overdrive is no longer functioning properly? If that’s the case, should I stop pressing that little button?
That’s certainly possible. If that’s the case, you can either choose to have it repaired (possibly very expensive–OD trannies cost nearly double what a non-OD one does), or just turn it on when you’re on the highway.
My knowledge of Volvos is very limited (owned a '77 one for six months), but from the quote above, I’m wondering if it’s possible that Volvo used an external overdrive. Maybe something along the lines of a Gear Vendors aftermarket unit? No help for the OP, just an additional question.
