What is overdrive and why leave it on all the time?

[BKSinAZ]

What is overdrive and why leave it on all the time? My 2001 4RUnner owners manual states to leave it on. What would be a situation that I would not want overdrive on? I drive mostly to and from work at speeds under 55, would I use more gas with it on? If it needs to be on all the time, why have the option to turn it off?

:50cal:

 

[Auburn 4Runner]

Overdrive is your top-end gear and should be left on when driving at high speeds so as to not put as much strain on your engine. It is "basically" 4th gear on your model I believe. Some people take overdrive off in certain situations such as passing cars and other instances where higher rpms are needed. So basically when it is off it drops down a gear and when turned back on it shifts back into overdrive.

 

[02sport]

I'd say leave it on for fuel economy. the only reason i would think to turn it off is maybe towing, or if goin up a slight grade, and the transmissison keeps hunting for the right gear....

 

[Thai]

In most cars, the OD gear is the last one...in your 4runner, it's the 4th gear. Let's talk about gear ratios:

1st gear = 2.8
2nd gear = 1.6
3rd gear = 1.0
4th gear = 0.7

Above is just an example. As you can see, the first 3 gears have ratios greater than or equal to 1.0. This means that acceleration is good in those gears (best in 1st gear, next 2nd, and so on). Another way to think is that 1st gear multiplies the torque by 2.8; while 2nd gear multiplies it by 1.6; and so on.

So, because of more torque, your 4runner is stronger in the first three gears (again, strongest in 1st gear).

Now, the 4th gear...aka OverDrive gear. The 4th gear is LESS THAN 1.0. So, acceleration is not gonna be good...again, think about torque multiplication...since it's less than 1.0, your torque rating is actually LESS.

Why is it good then?? Well, when you cruise on the highway, you don't need that much power, right? So, by having the overdrive gear, your engine is not stressed and is relaxed. Less strain on your powertrain. Quieter. Most importantly, IT SAVES FUEL because you are not using too much of your engine.

What does your 4runner do when you want to pass someone on the highway?? Well, your 4runner DOWNSHIFTS to 3rd gear for MORE POWER to help you pass. Then, when you pass the car and crusing again, the transmission upshifts back to 4th gear (again, less powertrain stress, quieter, and saves fuel).

In my opinion, you should ALWAYS leave your OD on. Let the computer do the thinking for you. OD is good. Saves fuel. Less stress on powertrain.

The ONLY time that you would want to turn it OFF is when you are TOWING. In addition to putting stress on powertrain, towing is nasty on the TORQUE CONVERTER. If you tow something heavy and your transmission is in OD, then you're killing the torque converter. So, when towing, it is advisable to TURN OFF OD.

A few people will turn off OD during rush hour traffic to decrease the shifting (that is, tranny shifts thru 3 gears instead of 4...thus, more responsiveness)...for me, i really don't see much point in that.

A few people may also turn off OD during off-roading. For me, you will never go fast enough for a period of time for the tranny to shift to OD...so, again, i don't see much point in that.

Basically, LET THE TRANSMISSION COMPUTER do the thinking for you. ONLY when you tow something should you turn off OD.

Hope this helps.

 

[BKSinAZ]

This is what I've noticed at lower speeds

In most cars, the OD gear is the last one...in your 4runner, it's the 4th gear. Let's talk about gear ratios:

1st gear = 2.8
2nd gear = 1.6
3rd gear = 1.0
4th gear = 0.7

Above is just an example. As you can see, the first 3 gears have ratios greater than or equal to 1.0. This means that acceleration is good in those gears (best in 1st gear, next 2nd, and so on). Another way to think is that 1st gear multiplies the torque by 2.8; while 2nd gear multiplies it by 1.6; and so on.

So, because of more torque, your 4runner is stronger in the first three gears (again, strongest in 1st gear).

Now, the 4th gear...aka OverDrive gear. The 4th gear is LESS THAN 1.0. So, acceleration is not gonna be good...again, think about torque multiplication...since it's less than 1.0, your torque rating is actually LESS.

Why is it good then?? Well, when you cruise on the highway, you don't need that much power, right? So, by having the overdrive gear, your engine is not stressed and is relaxed. Less strain on your powertrain. Quieter. Most importantly, IT SAVES FUEL because you are not using too much of your engine.

Hope this helps.

When doing 45 mph, I experimented by switching off the OD and I noticed that the RPMs jumped up about 10 - 15.

Whats your take on that?

By the way, I drive a 2001 4Runner with 4WD so what generation is that?

 

[Thai]

If you're cruising at 45 mph, then your transmission is in 4th gear (OD gear). Thus, when you turn it OFF, your transmission shifts OUT OF OD and into 3rd gear...explaining your jump in RPM...aka, when you turn off OD, you're DOWNSHIFTING into 3rd gear.

3rd gen 4runners run from 1996-2002.

 

[BKSinAZ]

Thank you

nt

 

[peter78]

The times I turn off the overdrive:

1.) Towing- overdrive tends to overheat the transmission.
2.) Hilly terrrian-going up and down hills or taking a long uphill or down hill climb.
3.) Hunting-I am talking about going from one gear to another. I take the overdrive off.
4.) Passing-When I am behind a car on a two lane road I shift to a lower gear before I pass to get a little extra oomph.
5.) Bad Codition-When it is sleet or ice or heavy rain I slow down and keep it in 3rd gear.

 

[Wonderso]

In most cars, the OD gear is the last one...in your 4runner, it's the 4th gear. Let's talk about gear ratios:

1st gear = 2.8
2nd gear = 1.6
3rd gear = 1.0
4th gear = 0.7

Above is just an example. As you can see, the first 3 gears have ratios greater than or equal to 1.0. This means that acceleration is good in those gears (best in 1st gear, next 2nd, and so on). Another way to think is that 1st gear multiplies the torque by 2.8; while 2nd gear multiplies it by 1.6; and so on.

So, because of more torque, your 4runner is stronger in the first three gears (again, strongest in 1st gear).

Now, the 4th gear...aka OverDrive gear. The 4th gear is LESS THAN 1.0. So, acceleration is not gonna be good...again, think about torque multiplication...since it's less than 1.0, your torque rating is actually LESS.

Why is it good then?? Well, when you cruise on the highway, you don't need that much power, right? So, by having the overdrive gear, your engine is not stressed and is relaxed. Less strain on your powertrain. Quieter. Most importantly, IT SAVES FUEL because you are not using too much of your engine.

What does your 4runner do when you want to pass someone on the highway?? Well, your 4runner DOWNSHIFTS to 3rd gear for MORE POWER to help you pass. Then, when you pass the car and crusing again, the transmission upshifts back to 4th gear (again, less powertrain stress, quieter, and saves fuel).

In my opinion, you should ALWAYS leave your OD on. Let the computer do the thinking for you. OD is good. Saves fuel. Less stress on powertrain.

The ONLY time that you would want to turn it OFF is when you are TOWING. In addition to putting stress on powertrain, towing is nasty on the TORQUE CONVERTER. If you tow something heavy and your transmission is in OD, then you're killing the torque converter. So, when towing, it is advisable to TURN OFF OD.

A few people will turn off OD during rush hour traffic to decrease the shifting (that is, tranny shifts thru 3 gears instead of 4...thus, more responsiveness)...for me, i really don't see much point in that.

A few people may also turn off OD during off-roading. For me, you will never go fast enough for a period of time for the tranny to shift to OD...so, again, i don't see much point in that.

Basically, LET THE TRANSMISSION COMPUTER do the thinking for you. ONLY when you tow something should you turn off OD.

Hope this helps.

Is this all the same and sound advice for my 1990 4Runner?