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Car Forum / Volvo Cars / May 2007What does the overdrive do?
I just bought a 1989 Volvo 740 GL and it has that button for the overdrive. What does it do? and when should I use it? I know this is probably a stupid question, but I would still much appreciate an answer. I'm sure whatever it is, it's only half as endearing as the hand cranked sunroof. >I just bought a 1989 Volvo 740 GL and it has that button for the > overdrive. What does it do? and when should I use it? I know this > is probably a stupid question, but I would still much appreciate an > answer. I'm sure whatever it is, it's only half as endearing as the > hand cranked sunroof. In an earlier contribution to this discussion, > I just bought a 1989 Volvo 740 GL and it has that button for the > overdrive. What does it do? and when should I use it? I know this > is probably a stupid question, but I would still much appreciate an > answer. I'm sure whatever it is, it's only half as endearing as the > hand cranked sunroof. It's an additional 2-speed gearbox behind the main gearbox. When it's Off, the main gearbox output drives straight through to the axle. When the overdrive is engaged, it provides a higher gear than normal top gear - useful for quieter cruising and improved fuel economy. I don't know anything about the overdrive used by Volvo but overdrives in general can usually only be engaged when the main gearbox is in top gear (plus maybe the next one down).  SignatureCheers, Roger ______ Email address maintained for newsgroup use only, and not regularly monitored.. Messages sent to it may not be read for several weeks. PLEASE REPLY TO NEWSGROUP! >I just bought a 1989 Volvo 740 GL and it has that button for the > overdrive. What does it do? It is an extra little gearbox with one gear and a little clutch outside the 4 gears-gearbox. It can be engaged only when you are in forth gear. The 4 gears are shifted mechanically, the overdrive is controlled by a solenoid and oil pressure when you press the button in 4th gear. It is practically a 5th gear. >and when should I use it? You use it like a 5th gear as soon as you have reached the rpms when you would change gear with a 5 gears manual gear box. Be sure to use the clutch before pressing the button. When you want to shift back to gear 4, press clutch again and press button again. When you are in gears 1, 2, 3 the overdrive can not be engaged. The overdrive is also controled by a relay near the fuses. > answer. I'm sure whatever it is, it's only half as endearing as the > hand cranked sunroof. did you mean enduring? I have one with 376.000 km. The only thing I have replaced is the relay some time ago. http://en.wikipedia.org/wiki/Overdrive_%28mechanics%29 gives more info. Viktor Hi, VladicRavich@gmail.com schrieb: > I just bought a 1989 Volvo 740 GL and it has that button for the > overdrive. What does it do? As already mentioned, the OD is sort of a 5th gear. IIRC the manual suggests not to apply (too much) power while engaging and slightly press the clutch while disengaging th OD for smooth operation. Roland On May 21, 12:58 pm, VladicRav...@gmail.com wrote: > I just bought a 1989 Volvo 740 GL and it has that button for the > overdrive. What does it do? and when should I use it? I know this > is probably a stupid question, but I would still much appreciate an > answer. As others said it is nothing more than another gearbox added to the back of the standard transmission. The Laycock de Normanville unit has been used in a wide variety of cars. > I'm sure whatever it is, it's only half as endearing as the > hand cranked sunroof. I'm confused by this statement. The overdive unit is in my experience very reliable. And the hand cranked sunroofs in two of my earlier cars were quite reliable too. Thought for the day: Older Volvos have a way of combining endearing and enduring into one. > On May 21, 12:58 pm, VladicRav...@gmail.com wrote: > > I just bought a 1989 Volvo 740 GL and it has that button for the [quoted text clipped - 12 lines] > very reliable. And the hand cranked sunroofs in two of my earlier > cars were quite reliable too. > On May 21, 12:58 pm, VladicRav...@gmail.com wrote: > > I just bought a 1989 Volvo 740 GL and it has that button for the [quoted text clipped - 12 lines] > very reliable. And the hand cranked sunroofs in two of my earlier > cars were quite reliable too. If you desire a "normal" fuel economy it is only used when towing, climbing hills and possibly passing. Keeping it on will lower your gas mileage since you will be in a lower gear.. hope helps...have fun....sno SignatureNo matter how dangerous nuclear power may or may not be..... Is it any more dangerous then what we are doing now.....??? This tag line is generated by: SLNG (Silly Little Nuclear Generator) >I just bought a 1989 Volvo 740 GL and it has that button for the > overdrive. What does it do? and when should I use it? I know this > is probably a stupid question, but I would still much appreciate an > answer. I'm sure whatever it is, it's only half as endearing as the > hand cranked sunroof. Since this car is an '89 and has overdrive, it has an automatic transmission so the other replies you've had so far are not correct for this car and only apply to pre-'87 manual transmission cars. The overdrive button on your '89 disables the 4th gear on the transmission. When you engage the overdrive lockout, a yellow arrow will illuminate in your instrument cluster and the transmission will function as a 3 speed unit, never shifting into the top gear. This is useful occasionally when going up long hills or when towing a trailer where the transmission may hunt, shifting back and forth between 3rd and 4th with annoying frequency. 99.9% of the time you'll just want to leave the overdrive lockout disengaged. > The overdrive button on your '89 disables the 4th gear on the transmission. > When you engage the overdrive lockout, a yellow arrow will illuminate in [quoted text clipped - 4 lines] > 99.9% of the time you'll just want to leave the overdrive lockout > disengaged. I am getting confused. I have an 88 GLE automatic. I run with it all the time without the Yellow up arrow illumenated in the dash. Is that the way, it should be? I should have the arrow illuminated while climbing a mountain or going up a steep hill tough, right? > > The overdrive button on your '89 disables the 4th gear on the transmission. > > When you engage the overdrive lockout, a yellow arrow will illuminate in [quoted text clipped - 13 lines] > I should have the arrow illuminated while climbing a mountain or going > up a steep hill tough, right? You got it....think of it as downshifting to a lower gear in a manual when you hear the engine starting to lug....it does the same thing.. and the arrow will be on at this time... hope helps....have fun....sno SignatureNo matter how dangerous nuclear power may or may not be..... Is it any more dangerous then what we are doing now.....??? This tag line is generated by: SLNG (Silly Little Nuclear Generator) In an earlier contribution to this discussion, >> I just bought a 1989 Volvo 740 GL and it has that button for the >> overdrive. What does it do? and when should I use it? I know this [quoted text clipped - 15 lines] > leave the overdrive lockout > disengaged. I've no doubt that you are right - but it seems very odd to call this 'overdrive' when it is, in fact, exactly the opposite! Or is it actually labelled 'overdrive lockout' or somesuch - on the basis that the 4th gear is considered to be an overdrive, and this button prevents it from being engaged? My previous reply related to the conventional definition of overdrive, usually - though not exclusively - fitted behind manual transmissions. SignatureCheers, Roger ______ Email address maintained for newsgroup use only, and not regularly monitored.. Messages sent to it may not be read for several weeks. PLEASE REPLY TO NEWSGROUP! Hi, Roger Mills schrieb: > I've no doubt that you are right - but it seems very odd to call > this 'overdrive' when it is, in fact, exactly the opposite! Well, since we had also a 760GLE long time ago, I remember now the button. I think, it wasn't labelled at all... ;-) Roland > In an earlier contribution to this discussion, > [quoted text clipped - 26 lines] > My previous reply related to the conventional definition of overdrive, > usually - though not exclusively - fitted behind manual transmissions. Overdrive, fourth gear, fifth gear, another gear,... call it what you want. Whatever you call it, it's engaged by default when you start the car (assuming all is functioning as designed) and can be disengaged by pressing the button or romping on the gas. Presumably, this 'on by default' helps score better EPA/mileage ratings. Although I've never heard or read the same about Volvos, Chevy used to recommend disengaging their OD when putting around town as (their) OD slows everything down in the transmission, including the pump, and could cause excessive heat build up. ymmv. > In an earlier contribution to this discussion, > [quoted text clipped - 26 lines] > My previous reply related to the conventional definition of overdrive, > usually - though not exclusively - fitted behind manual transmissions. It's not labeled as anything, it's a plain black button, and pushing it illuminates the yellow arrow symbol and disables the automatic overdrive. I forget what they call it in the owner's manual, but it does describe what it does and how to use it. Overdrive, by definition, is a gear in which the output shaft of the transmission rotates faster than the input shaft, the term has no bearing on whether the transmission is automatic or manual or how the mechanics of it function. In an earlier contribution to this discussion, > Overdrive, by definition, is a gear in which the output shaft of the > transmission rotates faster than the input shaft, the term has no > bearing on whether the transmission is automatic or manual or how the > mechanics of it function. I have no problem with that. What I *do* have some difficulty with is the concept of a so-called 'overdrive' button which *prevents* the overdrive from functioning! SignatureCheers, Roger ______ Email address maintained for newsgroup use only, and not regularly monitored.. Messages sent to it may not be read for several weeks. PLEASE REPLY TO NEWSGROUP! > In an earlier contribution to this discussion, > [quoted text clipped - 7 lines] > What I *do* have some difficulty with is the concept of a so-called > 'overdrive' button which *prevents* the overdrive from functioning! So, you have a problem with a button that disengages the overdrive when you push it... but no problem with a pedal that disengages the transmission when you push it? Ok... In an earlier contribution to this discussion, >> In an earlier contribution to this discussion, >> [quoted text clipped - 12 lines] > transmission when you push it? > Ok... I may do if it were called a 'drive' pedal. <g> I guess it's a case of usage. The only overdrives I've come across in the UK have had a button to *engage* them - the default when not pressed being 1:1 drive. So the concept of having the overdrive engaged by default, and needing a button to *disengage* it is somewhat foreign to me. SignatureCheers, Roger ______ Email address maintained for newsgroup use only, and not regularly monitored.. Messages sent to it may not be read for several weeks. PLEASE REPLY TO NEWSGROUP! > I guess it's a case of usage. The only overdrives I've come across in the > UK have had a button to *engage* them - the default when not pressed being > 1:1 drive. So the concept of having the overdrive engaged by default, and > needing a button to *disengage* it is somewhat foreign to me. "Overdrive lockout" or "overdrive defeat" is perhaps a better term. You could also call it 4th gear lockout, semantics aside, it's a feature common to virtually every automatic transmission made in the last couple decades. Some you push a button, some you move the gear selector from D to 3, it all really does the same thing, limiting the highest gear the transmission will shift into. I haven't seen a non-overdrive slushbox since the late 1970s. > In an earlier contribution to this discussion, > [quoted text clipped - 21 lines] > drive. So the concept of having the overdrive engaged by default, and > needing a button to *disengage* it is somewhat foreign to me. What peeves me about it is it's on by default but when it fails, it fails in the disengaged mode. The old four banger really sings when it drops out of overdrive at 80 mph. Anyway, it's all about "fuel economy." The manufacturers can get a better highway rating if it's on all the time. I remember when the Z1 Corvette first came out with it's fancy 5 or 6 or 7 speed manual. GM built in a system that forced you to shift from first to third (locked out second gear) unless you wound it past a certain RPM in first. GM got a better MPG rating and drivers got pissed. Funny story: When Car and Driver tested the new Vette and discovered this 'feature', they asked one of the GM techs that was there for the test how to disable it. Of course, they weren't allowed to reveal how to disable it but they did offer that 'there's a wiring harness coming out of the transmission and whatever they did, they should not cut the red one'... or words to that effect. It's been a lot of years. |
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