Overdrive

[Timw286]

I've never used overdrive before, and I've had it on my last 4 cars. I was playing with in it tonight and don't really understand what its for. I noticed while cruising at a steady speed and your turn OD off, the RPM's jump up quick. Is it compareable to downshifting in a manual? What is it for exactly? Passing? Racing?:confused:

[NXSBOB]

i've never used overdrive before, and i've had it on my last 4 cars. I was playing with in it tonight and don't really understand what its for. I noticed while cruising at a steady speed and your turn od off, the rpm's jump up quick. Is it compareable to downshifting in a manual? What is it for exactly? Passing? Racing?:confused:

dahhhhhhhhhhhhh !!!!!!!!!!!

[Mr. Man]

I've never used overdrive before, and I've had it on my last 4 cars. I was playing with in it tonight and don't really understand what its for. I noticed while cruising at a steady speed and your turn OD off, the RPM's jump up quick. Is it comparable to downshifting in a manual? What is it for exactly? Passing? Racing?:confused:


dahhhhhhhhhhhhh !!!!!!!!!!!
What NXSBOB meant to say is it is primarily used to conserve fuel. Drive or 3rd in our 4 gear auto is a 1:1 and OD lowers the 1st number to below 1. I'm not sure of the OD ratio. If you are racing it is best to turn the OD off.

People who ask questions here should not be ridiculed. I'm sure if Tim286 knew what the answer was he wouldn't have asked the question. Someday you'll ask a question and I'm sure you'd be miffed if the first response you got was Dahhhhhh and it's Duh anyways.

[MyBlackBeasts]

I've never used overdrive before, and I've had it on my last 4 cars. I was playing with in it tonight and don't really understand what its for. I noticed while cruising at a steady speed and your turn OD off, the RPM's jump up quick. Is it compareable to downshifting in a manual? What is it for exactly? Passing? Racing?:confused:

What overdrive means is the final gear turns the trans output shaft faster that the engine rpm. IE for 1 engine revolution the trans output shaft may turn 1.25 times (depends on o/d ratio). In a non-o/d trans (or 3rd gear in this trans) the ratio is 1 to 1, 1 engine rpm = 1 trans output shaft rpm. The o/d is designed to increase fuel mileage as the engine runs at a lower rpm for the mph you are driving. (Compare the engine rpm on tach at 55mph with o/d on & off and you can see the difference) When driving in city speeds (say 35mph or less) you want to have o/d off to prevent excess shifting which wears the trans. When towing/pulling a load you want the o/d off to prevent trans overheating and excess wear. When driving 35/40+ mph normal, keep o/d on to get the best fuel mileage. It also gives you a faster top end speed. :burnout:

[Timw286]

Thanks Mr. Man and MyBlackBeasts for the input and not responding with a mispelled, one word sarcastic answer. I appreciate it and look forward to messing around with OD.

[WI Fordguy]

Also, you don't have to pull start most cars these days....you can, but you don't have to.

[71cyclone]

Overdrive in a 5-speed mustang is a .75 ratio 4th gear is a 1.0 ratio so if you have a 3.55 rear end ratio you take ---3.55 and multiply it by .75 and your final drive ratio will be around 2.66 final drive ratio [saves fuel ]

[RF Overlord]

Tim, to summarise:

Higher ratios provide an increase in power at the expense of top speed.
Lower than 1:1 ratios provide more speed at the expense of power.

in the 4R70W transmission we have, the ratios are:
1st: 2.84 :1
2nd: 1.55 :1
3rd: 1.00 :1
4th: 0.70 :1
Rev: 2.23 :1

So you can see that 4th is the overdrive. It's primarily used to provide an increase in fuel economy at highway speeds, although the transmission in our cars is (unfortunately) tuned to get into the higher gears, including OD, as quickly as possible, which is not the best for spirited driving. A lot of people leave OD off when just driving around town and only engage it on the highway.

One thing is important: DO NOT floor the accelerator (like to pass someone) with the car in OD. Doing so is very tough on the OD band and eventually will cause failure. Cancel OD with the shifter button first, then go ahead and mat it.

[Timw286]

Alright thanks, I was just curious with the RPM's jumping up and down while engaging the OD. I'm a pretty conservative driver for the most part so I'll just leave it be, thanks for the info RF.

[Chevyguy]

I think everyone is confused about the question..

The OD/Off button is for locking out the overdrive gear (4th in our cars)

The old skool AOD and GM trans had the shift pattern of PRN (OD) D321 (Some fords have no 2 or 1 position)

With clunky column shifters it's difficult to shift from od to 3rd gear without hitting second, so with the advent of the electronic shifting Ford and most other manufacturers switched the OD function to a lockout button. Vastly easier to deal with put in drive and go. If you run into a reason to shift out of OD just push the button.

[ctrlraven]

It's just meant for a cruising gear. If you do a lot of highway driving or steady mph driving it will help increase gas mileage since the motor is turning at less rpms.

When you take it out of OD or turn it off, all it's doing is downshifting into 3rd gear.

Lets say you are on the highway and you want to pass someone, turn off OD and give it some gas. Also another important thing to remember if you ever go Wide Open Throttle (mash the gas pedal to the floor) make sure you have OD turned off. Down shifting from 4th to 2nd (when OD is not turned off and you go WOT while cruising) it will wear heavily on the OD band. Turn OD off (kicks down to 3rd) and then go WOT it only down shift to 2nd which is still wear on the trans but a whole lot less.