Overdrive vs regular drive

Whats the difference?

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Greetings,
Not getting into the technical details of the internal workings of the transmission, the difference is the rate at which the rear wheels will turn in relation to engine speed. This is known as final drive ratio. In OD, the rear wheels turn slightly faster for the same engine RPM as in Drive.
There are a few ways that this is done - an extra gear, a lock-up torque converter, etc. Others here are more qualified than I if you want a detailed explanation. Depending on the set-up of the drive train, OD may also lower your towing/hauling capacity, but may increase your top speed and MPG while unloaded.
Cheers - Jonathan

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Jonathan wrote:

Close, basically it is another gear after drive. Drive is 1 to 1 (one engine rev to one output shaft rev) and OD on a automatic is usually in the .7 to .75 to 1 range (dependend on brand) so engine turns 25 to 30% percent slower when it is engaged in a effort to save a little fuel in most cases when vehical is lightly loaded and on fairly flat ground.
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thanks for the posts
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Gear ratio.

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overdrive has gears that are about 33% higher and give you lower rpms on the highway for better mileage, but less power. to be used only on flat drives with any load. old john

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snipped-for-privacy@comcast.net wrote:

I would not say any load. With some vehicles it has to be a very light load
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Overdrive means the final gear ration is lower than 1/1 ratio. A OD tranny generally gives you better fuel mileage because you run the engine at a lower RPM. Early chevy OD transmissions were somewhat problematic but todays 4L60 is a dependable beast and when you do have problems its a cheap and easy rebuild. if you can avoid 87 and earlier 4l60 and 700r4. Also avoid towing in OD because the 2/4 band won't stand up to it, if you tow simple pull it down to drive.

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