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Car Transmission

Increase gear or transmission band to save fuel
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I have lost my 4th "gear" on my volvo 740GL, and now I am spending more on fuel, but going at 60 rather than 70mph on the motorway. Why not manufacture transmission systems with extended gear ratios. Vehicles would use less fuel and would emit less noise. eight gears would be fun as well.

Uked

uked, Dec 28 2002

Simulate a whole bunch of gears http://www.technofile.com/cars/cvts.html
Continuously Variable Transmission. Offers the added benefit of running the engine in a very small RPM range. [half, Oct 17 2004]

[link]






       Line forms here
thumbwax, Dec 28 2002
  

       Some production cars coming out soon (I believe the new Ferrari Enzo already has it) have 7-speed manuals, and I imagine more gears will be added as the companies want to go faster/conserve fuel/have bragging rights/so on.
Bert6322, Dec 28 2002
  

       Performance cars, particularly racing cars, have more gears than than regular cars because their engines tend to deliver power in a narrow rev band; or rather, the intention is to use just the high part of the power curve so they have more gears to enable this.
I assume that "extended gear ratios" implies a higher top gear not just more interpolated ratios; the solution is an added overdrive unit; these are rare now, but were quite common in the sixties, and I had two Triumphs which had such units fitted. They had a ratio of 0.797:1.
I'm somewhat interested to know how you can "lose" 4th gear without the entire box being trashed. Is it manual or auto?
angel, Jan 02 2003
  

       Continuous gearing is the way to go.
FloridaManatee, Jan 02 2003
  

       Brummm.. brummmm.   

       Actually, gearing is developed not for reasons of speed, but torque to make it easier on de/inclines. That's why the UK doesn't like automatic shift - not much good on hills and windy roads.
kpx, Jan 02 2003
  

       thanks Angel and everyone else for some very interesting reading, still to digest.   

       My Volvo (1990) is automatic, and I "lost" the 4th gear, it started gradually, during motorway driving. I thought that it was something to do with stress on the engine. The transmission works ok otherwise. My garage said that it wasn't worth trying to get it repaired, as repaired transmissions often fail later. I was told that it could go on or just fail
uked, Jan 02 2003
  

       That is the concept behind the overdrive transmission. As UnaBubba said, gear'm too high, and acceleration is lost. Then you'd have to have a bigger engine, and well....you know the rest of that. Most cars today don't make very good torque, compared to older engines, because modern cars have smaller displacements, and have to rev higher to do the same amount of work.
Darknight, Jan 02 2003
  

       Freaky. The same thing happened to my Uncle's earlier model automatic transmission Volvo. He lost a gear (sounds like 4th), then on the way home ... all other gears. Finally ground to a halt at the bottom of his road. No transmission fluid remained. He scrapped it and bought a Beemer.   

       Sounds like you need an urgent service or a new car, not extra gears.
FloridaManatee, Jan 03 2003
  

       Being a Volvo owner Darknight, I was thinking of being able to just drift along, almost as if coasting, to save fuel. never mind the acceleration.   

       I also feel that I need a vehicle thats solid, almost like a tank, for security whilst driving, the Volvo does the job. Strange that have not noticed any diesel Volvos other than trucks.
uked, Jan 03 2003
  

       I had lost what I think was second on an old car of mine. Which meant driving at low speeds made my engine terribly loud. no fun at all.
notme, Jan 03 2003
  

       [Bert6322] I'd hardly define the Enzo as a production car, its only really a way for Ferrari to show off what we already know. You'll never be able to get one of their cars.
kaz, Jan 03 2003
  

       Uked, that sounds like a nice idea. I wish it were workable, but sometimes you really need acceleration to avoid an accident. I think the biggest gains are not in improving the transmission, but eliminating it. The transmission zaps about 15-20%of the efficiency automatically...so to speak. Then we have the engine, which might get 35% efficiency, at the very best. As you can see, those numbers aren't very good at all. The right engine will be more efficient on its own, and also need no transmission. How to do that? I leave that for you to ponder, but meanwhile, I'm working on it.
Darknight, Jan 03 2003
  

       What's a beamer?
uked, Jan 04 2003
  

       A relative of mine once built a beach buggy with a weber-fed ford crossflow motor and hooked up a 3 stage auto truck gearbox to the end of the ford 4 speed. Was bizarre to drive as you had a second gear shift lever to work. The result was 13 forward speeds. No, i'm not trying to say 4x3 does not equal 12. If you put the first gearbox in reverse, and the second in reverse you end up with an aditional forward speed! But an aditional gearbox/transfer case in most cars with perhaps 2-3 ratios that could be economy, sport, and towing.
venomx, Feb 10 2003
  

       Bimmer.
"Line forms here" at the outset was indication that extra gears are widely baked. e.g. 6 gears in production Audi.
<commaless>Tip'o'day: The UKers in a Saab group I'm in who've owned both Saabs and Volvos recommend the Bentley repair manual over the Haynes repair manual any day of the week.</commaless>
As it is doubtful you'd want to repair tranny your elf, in the meantime, I'd suggest a different, but reliable and recommended garage, since yours claims a repaired tranny "often fails later."
thumbwax, Feb 10 2003
  

       mmmm. fast food for thought... All big rigs (semi's big trucks) have 8+ speeds to help them get going.... also polaris fourwheelers have a cvt (continous varible tranny) honda came out a car with this too. The problem with a cvt is that they cant handle torque. The problem of putting more gears is the weight + size of the tranney would out weigh the performance gains
I2RI, Apr 07 2003
  

       If you are familar with Manual shifters you should realize that 5th gears have been added for just that reason. 5th gear is to have more economical Freeway driving. As with everything in life there is a limit as to how far you can take it. The more speed is increased the more drag you get => more gas you use.
jvanzand, Jun 16 2003
  

       try a 2 speed rear axle.
jotter, Jan 15 2004
  

       I have to assume the original problem was solved sometime in the past 3 years, but the original problem described sounded like a relatively common, and easily fixed problem. If nothing else, the entire transmission could be replaced. if the car is relatively new and in otherwise good shape this is economic, if it's old and crappy it might not, but generally, if a car is paid for it's much cheaper to repair the old rather than buy new.
whlanteigne, Sep 24 2005
  
      
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