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yact: When does overdrive kick in?

JEDI

JEDI

Lifer
Howstuffworks.com- Overdrive

My car is an automatic and has overdrive. Just curious at what RPM does it kick in.

The link tell me what overdrive is, but doesnt say when it kicks in.

So when does it kick in? and best way for me to keep it there?
 
Whenever your transmission's designer thoguht it was appropriate. It's not based solely on RPM, nor is it the same in every vehicle. Your car will be in overdrive when you're cruising on the freeway, that's essentially what it's there for. If yo uwant to keep it in overdrive, drive at normal freeway speeds without accelerating a lot.
 
for my car which is a maxima, with overdrive off what it does is lock out 4th gear. when overdrive is on the car will go into 4th gear.
 
OD is the last gear (though I think a few vehicles have two OD gears now) in the transmission. it simply means that it has less than a 1:1 ratio. So for every turn of the transmission, the engine turns less than once.
 
mine starts somewhere around 35 mph, maybe 40.

edit: actually its in overdrive at about 25 :Q
 
my car has 4 gears. so keeping it at 4th gear = max fuel efficiency?

so 25mpg school zones != max fuel efficiency since I'm not in 4th gear?
 
Originally posted by: JEDI
my car has 4 gears. so keeping it at 4th gear = max fuel efficiency?

so 25mpg school zones != max fuel efficiency since I'm not in 4th gear?
Click to expand...

Listen to how many shifts it makes.
 
Technically, overdrive is any gear where the ratio for the driven gear is less than one to one. Usually your tranny will only have one overdrive gear, though.
 
Just count the number of gear shifts. Be aware that if your tranny has a lockup torque convertor that when the convertor locks (usually after the tranny is in 4th gear) it will feel almost like another shift.
 
Originally posted by: iversonyin
I still don't understand what overdrive accomplish and does it have anything to do with gas mileage?
Click to expand...

overdrive is a gear where the output shaft of the transmission spins faster than the engine's crankshaft.

what it has to do with gas mileage is that if done correctly there isn't much additional torque left to accelerate, almost all of it is going to moving the car. in a lower gear the torque at the wheels is much higher so that the car can accelerate. but, if you're not accelerating all that additional torque is going to waste.
 
Whenever I put it in overdrive 😉

well technically my car has two overdrive gears.

4th - .96 or something.. barely overdrive
5th - .73
 
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