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O/D or 5th

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I'd assume he knows what OD stands for but doesn't know why it's marked as overdrive, when it probably was a true 5th gear.

Cars like the Europa Special that had a 5th gear were generally marked an 1-4 and OD, I guess it's because a lot of people still thought that way.

Andy

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I thought Overdrive meant a separate unit on the back of the gearbox - like on Triumph and MG + Others - then you could use it 3rd or 4th gear via an electric switch.

Did the Europa have a separate unit or a 5th gear inside the gearbox ?

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It was called an overdrive because that's exactly what it was. In that gear, the car was overdriven which is to say that the ratio was such that the car would reach maximum speed before reaching maximum power. A true top gear matches the two to get the theoretical highest maximum speed. So most sportscars would have a true top gear while the Esprit, as befits a grand tourer, had an overdriven 5th gear for quieter (and more economical) cruising.


S4 Elan, Elan +2S, Federal-spec, World Championship Edition S2 Esprit #42, S1 Elise, Excel SE

 

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I always thought an overdrive was any gear ratio where the engine revolutions were geared up to the final drive input...such as 0.9 to 1 as opposed to direct drive, top gear on normal boxes of 1 to 1. The Esprit is certainly faster in 5th than 4th, even though the gear ratio may be an "overdrive". Seperate overdrive units, as on lots of Triumph sportscars, are electrically actuated epicyclic gear units which produce more rotations on the output than the input, when actuated. Having re-read you post, Trevor, you're correct in that the Esprit won't pull max. rpm in 5th gear on the level..which would be pretty quick!!


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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All you need is a hill, Hilly...!!


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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I always thought an overdrive was any gear ratio where the engine revolutions were geared up to the final drive input...such as 0.9 to 1

This is what I have always known the definition of overdrive to be; less than one revolution of the engine to equal one revolution of the wheels. Reminds me how "oversquare" means less than one time the length of the stroke to equal one time the diameter of the bore.


Tony K. :)

 

Esprit S1s #355H & 454H

Esprit S2.2  #324J

1991 Esprit SE

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That defintion ignores the rear axle ratio, Tony. It should be that one revolution of the engine gives less than one revolution of the propshaft or the equivalent front-wheel drive terms.


S4 Elan, Elan +2S, Federal-spec, World Championship Edition S2 Esprit #42, S1 Elise, Excel SE

 

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