What is Overdrive in A/Ts?

**Kelso Hatch** · November 25th, 2002 02:39 PM

what about the "Power A/T hold" switch near the globe box?

**Ungas** · November 26th, 2002 03:36 PM

Sorry for the late reply sir, it took time to search for the right answers. :D

Here are some options of the power, hold and sometimes has a normal mode switch:

Power - Holds onto gears longer as well as down gears at much lower throttle positions.

Normal - Leaves the transmission in ADAPTIVE SHIFT mode. This means the car will put it self into power mode when it senses you are really pushing the car.

Hold - When this option is selected, the driver can literally use the automatic gear stick like a manual. This means that when you have the selector set to 2nd gear, the car will stay in second gear and ONLY second gear. Of course the car will change gears if necessary to avoid stalling.

**ice27** · May 7th, 2003 04:10 AM

sa a/t? how do you use it?

peace!!

**Karding** · May 7th, 2003 05:29 AM

pag naka OD mas smooth ang takbo ng car, specially sa highways. why? eto more technical definition ng OD:

Overdrive
By definition, an overdrive has a faster output speed than input speed. It's a speed increase -- the opposite of a reduction. In this transmission, engaging the overdrive accomplishes two things at once. In order to improve efficiency, some cars have a mechanism that locks up the torque converter so that the output of the engine goes straight to the transmission.

In this transmission, when overdrive is engaged, a shaft that is attached to the housing of the torque converter (which is bolted to the flywheel of the engine) is connected by clutch to the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothing is connected to the turbine; the only input comes from the converter housing. Let's go back to our chart again, this time with the planet carrier for input, the sun gear fixed and the ring gear for output.

Ratio = 1 / (1 + S/R) = 1 / ( 1 + 36/72) = 0.67:1
So the output spins once for every two-thirds of a rotation of the engine. If the engine is turning at 2000 rotations per minute (RPM), the output speed is 3000 RPM. This allows cars to drive at freeway speed while the engine speed stays nice and slow.

**B16ba-type-RSiR** · May 7th, 2003 05:35 AM

wher exactly are the other applications of overdrive?when going up or going down a hill??

**Karding** · May 7th, 2003 05:56 AM

I would assume not to engage OD uphill. Kse nung naka drive ako ng A/T with OD, pag pataas I do activate the OD para lakas hatak.

thats my experience...

**DeltaBravo** · May 7th, 2003 10:09 AM

experience ko lang

kapag O/D off naka set ang tranny sa 3 speed lang kaya kapag nasa highway ka at mabilis na ang sasakyan mo ay mataas din ang RPM kc nga limited ka lang for 3 speed lang ....kapag O/D on naka set naman for 4 speed and very usefull sa highway driving (mababa ang rpm dahil may 4th gear ka).....

kung pa downhill ka....ung D1 or D2....parang engine break na din....

**boybi** · May 7th, 2003 11:18 AM

for normal driving, O/D on.

sometimes naman, kapag nagovertake ka tapos nabitin ka, OD off mo.

**kimpOy** · May 7th, 2003 11:36 AM

tama ka delta bravo, so kapag city driving dapat naka off ka para up to 3rd gear ka lang

**sHoCkAbSoRbEr** · May 7th, 2003 12:35 PM

Overdrive (O/D) is the highest gear in the transmission. Usually on most cars, A/T has 3 speeds and O/D (forth speed). O/D allows the engine to have less rpm with higher speed in order to have better fuel efficiency. When you switch it on, you allow the transmission to shift into O/D mode after the certain speed is reached. Pag naka-off, you limit transmission shifting by third speed.

Pag normal driving condition the O/D should be always on. You may need to switch it off if you drive in mountains area.

You also may need to switch it off when you want to slowdown using the engine braking, for example, driving downhill.

Pero ako lagi lang naka-on O/D ko...

Nasa user's manual mo naman ata tong info na to... :wink: