Simon,
I'll have to defer to greater expertise than mine to debate this
further. My observations have always been, though, that one hears of an
OD unit but not an OD rear-axle gear.
BOb
On Thu, 07 Jan 1999 08:19:28 -0800 Simon Matthews
<simon_matthews@avanticorp.com> writes:
>I think your definition of what is an overdrive gear is wrong -- I
>don't
>believe it is simply a function of the ratio in the gearbox but rather
>I
>had always understood that an overdrive gear was one in which the
>overall
>gearing (engine to wheels) gave a higher gearing than the gearing
>required
>for top speed. In other words, the gearing is designed for comfortable
>cruising, not absolute top speed.
>
>Thus one can create an overdrive gear by changing the rear axle ratio.
>This
>definition allows a 1:1 top gear to be an overdrive gear.
>
>There is then the separate question of how many gears are required for
>convenient driving.
>
>Simon
>
>At 10:32 AM 1/7/99 EST, Bob Howard wrote:
>>Jerry,
>> For years and years, it was the practice to have top gear at 1 to
>1. An
>>overdrive unit was then bolted on in order to achieve the OD ratios,
>.87
>>to 1 or whatever.
>> Making the top gear with an OD ratio is a simpler and less
>expensive
>>way to achieve the desired ratio.
>>Bob
>>
>>On Wed, 6 Jan 1999 20:24:34 EST GMGoodman@aol.com writes:
>>>I have seen the use of 5 speed transmissions with the Midget--and
>some
>>>discussion of 5 speeds in Bs---but today I had a thought which
>crossed
>>>my
>>>mind. Help me out -----I have always been under the impression that
>
>>>no matter
>>>how many gears you have, the final gear is 1 to 1. That is for
>every
>>>turn on
>>>the input side, you get one turn at the rear. Sooooo how is it
>that
>>>a 5
>>>speed has the effect of an overdrive -----or does it? That is, lower
>
>>>rpms at
>>>high speed in the final gear. Example hihway driving. I'm
>>>puzzled----------guessI don't understand what I thought I did.
>>>
>>>Your thoughts please Jerry G '72 B
>>>
>>
>>
>>
>---
>Simon Matthews
>MailTo:simon_matthews@avanticorp.com
>'57 MGA
>
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