O/D Button?

[Bstang03]

I've been looking around trying to figure out what exactly the O/D button does and there's a lot of different answers out there. What does it do exactly?

[67mustang97]

I believe all the O/D button does is change the shift points when it off It's more aggressive. (for power/towing)

[OsirisGuy]

Overdrive would be the 4th gear in the transmission. So when the overdrive is off the transmission only uses the 3 gears. It is similar to the 5th gear in manual transmission and that is for fuel efficiency (for example; it is a cruising gear).

The 2003 Mustang models use the 4R70W transmission which is an updated version of the AOD/AODE (AOD/E) transmission.
4 - # of gears
R - Rear Wheel Drive
70 - arbitrary number assigned by Ford to the transmission
W - Wide gear ratio*

*the wider gear is for the 1st and 2nd gear compared to the AOD/E.
-1st gear: 2.84:1 (2.40:1 in the AOD/E)
-2nd gear: 1.55:1 (1.47:1 in the AOD/E)
-3rd gear: 1.00:1 [Notice how in the 5-speed manual transmissions the one-to-one gear ratio is 4th gear]
-Overdrive (4th Gear): 0.70:1
-Reverse: 2.23:1

For comparison the Borg-Warner T5* gear ratios:
1st gear: 3.35:1
2nd gear:1.99:1
3rd gear: 1.33:1
4th gear: 1.00:1 [here is the one-to-one gear]
5th gear: 0.68:1 [this is the "cruising" gear]
Reverse: 3.15:1

*Numbers taken from Transmission Technologies Corp. and may not be 100% accurate (but may be close to the correct gear ratios, depending on vehicle specification).

[sonicpony03]

Yah, OsirisGuy gave you a nice technical explanation...good info.

Basically you don't have to worry about it too much. It won't really make the car faster or quicker than when it's off. The only thing you'll notice is a difference in sound...but while it may sound better, your mpg's are slipping because you are running at way higher rpms.

Instead of going 60 at 1800 rpms, you'll be going 60 at 2400 rpms.

[Bstang03]

My last car had 1,2,D3,D4,R,N,P and when I got my Mustang I noticed it didn't have the D3 option so I guess the O/D just replaces that.

[outlawfrog]

Yea, basically having it "off" will not be an advantage to you. In all of the AT's I've ever had, there was only ONE that it actually did anything but drop 4th. In my 2000 tacoma, I could turn it off.......run the tack up to about 3500-4000 in 3rd, then hit the clicky......it'd give me a VERY noticable boost before it hit 4th. Actually, I used it to pass my ex-wife's civic one night, just to piss her off even more, and lucky I'd already jumped back in the right lane before it chipped-out at 103! hehehe
But, keep in mind, that was a 4cyl. I've NEVER seen it do anything like that in a 6 or an 8.