Overdrive on or off?
06-28-2015, 12:14 PM
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Overdrive on or off?
Hey Yotatech people!
So, I've been driving my 95 4Runner for the last 5 months with the overdrive on. I just today thought "I should see if what it's like with overdrive off" and when I did, the engine felt much more responsive at higher speeds and almost felt like it went into lower gear. Is that what it's supposed to do? Is it easier on the engine and tranny to drive with it off or on?
So, I've been driving my 95 4Runner for the last 5 months with the overdrive on. I just today thought "I should see if what it's like with overdrive off" and when I did, the engine felt much more responsive at higher speeds and almost felt like it went into lower gear. Is that what it's supposed to do? Is it easier on the engine and tranny to drive with it off or on?
06-28-2015, 05:28 PM
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Your experience is normal. Overdrive is just what it says, it's an extra gear above the normal high gear. (Strictly speaking, it means the transmission output shaft is turning faster than the input shaft, rather than 1:1 as in a normal "high" gear).
So, overdrive allows your engine to run slower when cruising on the highway, saving wear and fuel. However, it will not be as responsive because of the higher gearing. Also, depending on the transmission, in overdrive the transmission "freewheels" on downhills, so engine braking is non-existent.
Normally, leave the overdrive on for level highway driving, and switch it off in the mountains or on slower curvy roads to prevent extra shifting and to have better engine braking.
So, overdrive allows your engine to run slower when cruising on the highway, saving wear and fuel. However, it will not be as responsive because of the higher gearing. Also, depending on the transmission, in overdrive the transmission "freewheels" on downhills, so engine braking is non-existent.
Normally, leave the overdrive on for level highway driving, and switch it off in the mountains or on slower curvy roads to prevent extra shifting and to have better engine braking.
06-29-2015, 09:20 AM
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06-29-2015, 02:53 PM
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Good to know. Most of my driving is either city traffic, or hilly highways, so I will be leaving it off. Thanks for the responses guys! The wealth of knowledge on these trucks in this forum is absolutely indispensable! Thank you all of for what you guys do!
There are really no hard and fast rules.Trending Topics
06-30-2015, 08:50 AM
#9
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Of course, whether or not to use OD all the time is a personal choice.
Thats why they put the button in.
Using it may even contribute to slightly greater fuel economy.
However,
Regular OD use in stop and go conditions has been shown to contribute to premature 3-4 clutch pack wear in some tranny types because of the excessive up and down shifting while operating in such conditions.
I just like the peppier performance from stoplight to stoplight with it disengaged.
To each their own.
Thats why they put the button in.
Using it may even contribute to slightly greater fuel economy.
However,
Regular OD use in stop and go conditions has been shown to contribute to premature 3-4 clutch pack wear in some tranny types because of the excessive up and down shifting while operating in such conditions.
I just like the peppier performance from stoplight to stoplight with it disengaged.
To each their own.
Last edited by millball; 06-30-2015 at 09:28 AM.
06-30-2015, 09:42 AM
#10
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Of course, whether or not to use OD all the time is a personal choice.
Thats why they put the button in.
Using it may even contribute to slightly greater fuel economy.
However,
Regular OD use in stop and go conditions has been shown to contribute to premature 3-4 clutch pack wear in some tranny types because of the excessive up and down shifting while operating in such conditions.
I just like the peppier performance from stoplight to stoplight with it disengaged.
To each their own.
Thats why they put the button in.
Using it may even contribute to slightly greater fuel economy.
However,
Regular OD use in stop and go conditions has been shown to contribute to premature 3-4 clutch pack wear in some tranny types because of the excessive up and down shifting while operating in such conditions.
I just like the peppier performance from stoplight to stoplight with it disengaged.
To each their own.
There's many millions of vehicles out there in stop and go traffic with overdrive on.
Don't hear stories about problems.
06-30-2015, 09:58 AM
#11
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They later discontinued this advice, not because the trannys had changed any, but because they knew that any problems would not occur until well after any warantees had expired, and because the extra time that the cars were operated in OD improved their MPG statistics for the EPA.
The various Jatco trannys can be found in some domestic cars, as well as in most imports except Toyotas and Honda. They are good trannys overall.
The years have showed that these trannys (F4-EAT is one) suffer shorter life when constantly run in OD in traffic. Specificly, the 3-4 clutch packs often fail prematurely.
Most still run well over 100,000mi, but have the potential to last very much longer if they are operated correctly. (OD off in traffic)
Last edited by millball; 06-30-2015 at 11:18 AM.
06-30-2015, 11:51 AM
#12
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I can tell you that in the 1990s', Ford/Mazda who used Jatco trannys, reccomended in their owners manuals, that OD not be used in traffic.
They later discontinued this advice, not because the trannys had changed any, but because they knew that any problems would not occur until well after any warantees had expired, and because the extra time that the cars were operated in OD improved their MPG statistics for the EPA.
The various Jatco trannys can be found in some domestic cars, as well as in most imports except Toyotas and Honda. They are good trannys overall.
The years have showed that these trannys (F4-EAT is one) suffer shorter life when constantly run in OD in traffic. Specificly, the 3-4 clutch packs often fail prematurely.
Most still run well over 100,000mi, but have the potential to last very much longer if they are operated correctly. (OD off in traffic)
They later discontinued this advice, not because the trannys had changed any, but because they knew that any problems would not occur until well after any warantees had expired, and because the extra time that the cars were operated in OD improved their MPG statistics for the EPA.
The various Jatco trannys can be found in some domestic cars, as well as in most imports except Toyotas and Honda. They are good trannys overall.
The years have showed that these trannys (F4-EAT is one) suffer shorter life when constantly run in OD in traffic. Specificly, the 3-4 clutch packs often fail prematurely.
Most still run well over 100,000mi, but have the potential to last very much longer if they are operated correctly. (OD off in traffic)
06-30-2015, 12:14 PM
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Like you said, that's why Toyota put the button there.
06-30-2015, 04:13 PM
#14
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The exact same principles apply, maybe the Aisin has more robust clutch packs, but nevertheless, unnecessary repetitive up-down shifting from using OD in other than higher speed cruising conditions leads to shorter component life.
How could it be otherwise??
How could it be otherwise??
Last edited by millball; 06-30-2015 at 05:01 PM.
07-01-2015, 04:54 PM
#15
I put a transmission temp gauge on my 95 4Runner with the a340h and the temp comes up a lot out of overdrive because the torque converter has a high stall speed so it generates a lot of heat. The stock radiator does not cool the tranny enough to run out of OD for long periods of time. I found that for pulling hills the ECT mode kept the transmission coolest and no matter what it is coolest in lockup with OD on. I would highly recommend always using OD as heat is the enemy of the auto trans
07-01-2015, 05:15 PM
#16
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I put a transmission temp gauge on my 95 4Runner with the a340h and the temp comes up a lot out of overdrive because the torque converter has a high stall speed so it generates a lot of heat. The stock radiator does not cool the tranny enough to run out of OD for long periods of time. I found that for pulling hills the ECT mode kept the transmission coolest and no matter what it is coolest in lockup with OD on. I would highly recommend always using OD as heat is the enemy of the auto trans
Pulling hills with OD locked out should help in a similar fashon.
Without a doubt, OD with converter lock-up should be coolest, because there is no hydraulic coupling to make fluid friction then, just pure mechanical coupling.
Where did you place your temp sensor and what kind of temps are you seeing??
Does your factory hi temp light ever come on??
Last edited by millball; 07-01-2015 at 05:18 PM.
07-01-2015, 06:36 PM
#17
When ECT is selected it stays in each gear longer but it will go into lockup in lower gears also while pulling hills where it actually doesn't in regular OD mode.
Yes my factory trans temp light came on climbing Donner summit in the Tahoe forest up until I installed an after market cooler at that point I installed an Autometer gauge on the output of the trans to the cooler. I no longer have had that issue but I have played with the different modes and have found where the transmission stays coolest as I posted above. If you turn off OD for anything longer than short intervals you will overheat the transmission from my experience.
Lockup temps are cruising 180 and up to 225 climbing hills going in and out of lockup with ECT. If you turn OD off they will continue to climb but if you leave OD on and use ECT the trans will shift again in 2nd and drop about 500 rpm and you will see the temp fall because the trans is in lockup around 3500 rpm. Without the cooler the dummy light came on so it hit 300. I highly recommend installing a gauge on the output back to the cooler. It gives you the highest temp that the transmission is getting up to.
Yes my factory trans temp light came on climbing Donner summit in the Tahoe forest up until I installed an after market cooler at that point I installed an Autometer gauge on the output of the trans to the cooler. I no longer have had that issue but I have played with the different modes and have found where the transmission stays coolest as I posted above. If you turn off OD for anything longer than short intervals you will overheat the transmission from my experience.
Lockup temps are cruising 180 and up to 225 climbing hills going in and out of lockup with ECT. If you turn OD off they will continue to climb but if you leave OD on and use ECT the trans will shift again in 2nd and drop about 500 rpm and you will see the temp fall because the trans is in lockup around 3500 rpm. Without the cooler the dummy light came on so it hit 300. I highly recommend installing a gauge on the output back to the cooler. It gives you the highest temp that the transmission is getting up to.
Last edited by Yotard; 07-01-2015 at 06:54 PM.
07-01-2015, 08:32 PM
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Well I just opened up a whole can of worms that I wasn't even planning on when I started this thread. 😂 Now anyway, this is all good to know. So when the ECT is on it stays in the lower gears longer even with the overdrive engaged? Does it do the same on hills? I drive on highway 4 here in California between Martinez and Richmond a lot, and if anyone on here has driven it before they know what I'm talking about. It's got some pretty steep inclines.
I've never used the ECT much, but does it have anything to do with better gas mileage like the overdrive does?
I've never used the ECT much, but does it have anything to do with better gas mileage like the overdrive does?
07-02-2015, 04:02 AM
#19
Yeah I live in Brentwood farther east on 4 I know that road well. As far as gas mileage goes I get 14 or 15 mpg no matter what. I climb Vasco road over to Livermore everyday which has some good grades on it as well. I am running 33" tires with 4.88 gears as well so I'm sure I am getting less because of that.
Yes when ECT is engaged it will stay in each gear longer, it just moves the shift points. It will also downshift sooner without applying as much peddle on hills.
If you take OD off then it will not go into overdrive ever whether you are in ECT or not.
If you have both OD on and ECT on you will find that the trans will down shift and RPMs will climb to around 4000 then you will get a slight shift and RPMs drop slightly like to 3500 maybe even 3700 and it still has power to climb the hill. If you are not in ECT mode it will not do that second shift into lockup from my experience.
That second little shift keeps the transmission temp from climbing but you still have power to climb the hill.
From my experience you only get that with ECT on and OD on.
I promise you that OD off is the worst for the heat don't do it. I highly recommend you add a tranny cooler also.
Yes when ECT is engaged it will stay in each gear longer, it just moves the shift points. It will also downshift sooner without applying as much peddle on hills.
If you take OD off then it will not go into overdrive ever whether you are in ECT or not.
If you have both OD on and ECT on you will find that the trans will down shift and RPMs will climb to around 4000 then you will get a slight shift and RPMs drop slightly like to 3500 maybe even 3700 and it still has power to climb the hill. If you are not in ECT mode it will not do that second shift into lockup from my experience.
That second little shift keeps the transmission temp from climbing but you still have power to climb the hill.
From my experience you only get that with ECT on and OD on.
I promise you that OD off is the worst for the heat don't do it. I highly recommend you add a tranny cooler also.
Last edited by Yotard; 07-02-2015 at 04:16 AM.
07-09-2015, 03:05 PM
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Yeah I live in Brentwood farther east on 4 I know that road well. As far as gas mileage goes I get 14 or 15 mpg no matter what. I climb Vasco road over to Livermore everyday which has some good grades on it as well. I am running 33" tires with 4.88 gears as well so I'm sure I am getting less because of that.
Yes when ECT is engaged it will stay in each gear longer, it just moves the shift points. It will also downshift sooner without applying as much peddle on hills.
If you take OD off then it will not go into overdrive ever whether you are in ECT or not.
If you have both OD on and ECT on you will find that the trans will down shift and RPMs will climb to around 4000 then you will get a slight shift and RPMs drop slightly like to 3500 maybe even 3700 and it still has power to climb the hill. If you are not in ECT mode it will not do that second shift into lockup from my experience.
That second little shift keeps the transmission temp from climbing but you still have power to climb the hill.
From my experience you only get that with ECT on and OD on.
I promise you that OD off is the worst for the heat don't do it. I highly recommend you add a tranny cooler also.
Yes when ECT is engaged it will stay in each gear longer, it just moves the shift points. It will also downshift sooner without applying as much peddle on hills.
If you take OD off then it will not go into overdrive ever whether you are in ECT or not.
If you have both OD on and ECT on you will find that the trans will down shift and RPMs will climb to around 4000 then you will get a slight shift and RPMs drop slightly like to 3500 maybe even 3700 and it still has power to climb the hill. If you are not in ECT mode it will not do that second shift into lockup from my experience.
That second little shift keeps the transmission temp from climbing but you still have power to climb the hill.
From my experience you only get that with ECT on and OD on.
I promise you that OD off is the worst for the heat don't do it. I highly recommend you add a tranny cooler also.
