Shifting An Auto Correctly

[NovaResource]

Originally Posted by MetalShark

OD is to keep the car at a lower RPM so you don't burn up as much gas.
some people say "keep on the OD to save gas" but all the shifting will really ware your transmission. best time to use it is if your taking long rides with as less braking as possible (the freeway).
all tho if your going for max speed OD kinda helps too. when your on your lasst gear about to max hit in OD and that will give some extra RPM.
OD does not make your car slower, but due to the lower RPM your acceleration will be slower.

GREAT SCOTT!!! Marty, did you leave the time machine on in the Delorean??

The original question was asked over 4 years ago!!

And to correct your answer, I must first discuss what overdrive really means.
Overdrive is nothing more that a gear ratio less than 1:1. For example: 1st gear might be 3:1 (3 engine revolutions for every 1 rotation of the trans output). Second gear might be 2:1 (2 engine revolutions for every 1 rotation of the trans output). Third might be 1:1 (1 engine revolution for every 1 rotation of the trans output).

But 4th gear (overdrive) might be 0.7:1 (.7 engine revolutions for every 1 rotation of the trans output). In this case, the trans output is spinning faster than the engine. In other words, it's being "overdriven".

Some manual transmissions have 2 overdrive gears (usually 5th and 6th gears).

Now, the OD ON/OFF button just means that it will or will not use the overdrive gear ratio. With OD ON, your have a 4 speed transmission with the overdriven gear ratio being used. With OD OFF you basically tell the transmission not to use the overdriven rear ratio so you now only have a 3 speed trans and it won't shift above 3rd gear.

The only reason I would turn the OD off is if you find the car struggling up a hill in 4th gear and constantly shifting between 3rd and 4th. What you do is turn it off and it will stay in 3rd gear allowing the engine to rev higher where it makes more power. You are basically downshifting to a lower gear ratio. Otherwise, always leave OD on.