jct61765

I just had a guy argue with me, almost violently, about when to use overdive. I dont tow anything, I always leave my O/D on. He says you have to shut it off below 40mph or it will toast your tranny. Oh, he has a Dodge Durango. We dont even have to talk about that. Does anyone here shut off their O/D under 40mph?

drguitarum2005

your friend has got it all wrong. in a typical automatic tranny, you have 3 speed gears and an overdrive gear, or 4th gear. under normal driving conditions, OD should be left on. period. overdrive, aka the 4th gear, usually gets engaged around 40 or so under normal conditions. turning OD off under 40 does absolutely nothing to your tranny, and it sure as hell isnt going to fry it. you should turn OD off when towing and in mountainous areas with hills etc.

Tanto

I _KINDA_ see where that moron with the dodge is coming from, but his statement in general is crap.

Where I see he's coming from is that the auto tranny will shift into O/D when it can maintain the speed you're going at, but if you are going through a hilly section or a lot of stop and go driving, disabling the O/D (and also turning on ECT) will reduce the shifts your transmission makes and therefore prolong the life of your transmission.

Don't ask that guy to help you with any issues with your vehicle.

kmchby76

Well I just learned something new. I'll keep in mind about turning off O/D when towing. Thanks.

ebelen1

There's another thread on here (that I can't find) talking about the same thing. I believe he has a point in that once your OD kicks in but your tranny has to downshift when you slow down or want to speed up, the constant shifting is building heat up in the tranny. What's the worst thing for a tranny? You bet, heat.

I decided to turn off my OD until I know I will be going over 45 mph consistently, most likely only on the freeway. This, like other things you try at first, feels like it's actually doing a good thing for your truck. I know at first, I felt like I had more power and a lot less shifting. I do know for a fact that it gained me 1 - 2 mpg. BTW, I only drive 5% on the freeways.

My mechanic buddy said the same thing but didn't want to argue w/ me so said "it's not always good to leave your tranny in OD, period." I think he was referring to this situation. Anyway IIRC, it was midiwall and a few others that had the true knowledge on this. Maybe, they'll chime in...

jrallan26

Around town, all driving below 40 mph I drive with the OD "off". Once over 40 mph OD is turned on.

drguitarum2005

the constant shifting of automatics when youre right between two gear ranges is why some people prefer a manual. yes the shifting creates heat and heat is bad, but its not like toyota (or any car company for this matter) doesnt know that that happens. their designs and tests have been altered accordingly. it is not something you need to be worried about. if you get a tranny cooler, the more power to you and youll extend the life of your tranny but it is not going to fry your tranny in any hurry. for this purpose, im using 40 mph as the point in which the OD gear kicks in. if youre driving around under 40 mph with OD on, you are using the first 3 gears. if you're driving around under 40 mph with OD off, you are using the first 3 gears. just simply having the button in our out under 40 mph does nothing to your transmission. its when you hit that 40 mph threshold that you will either shift into OD or rev up 3rd gear depending on if it is on or off. saying that turning it off under 40 mph will damage the tranny makes no sense seeing as how you dont hit that gear regardless.

EDIT: after reading that, i want to clarify that if you are driving around that threshold speed (40 mph for this argument), its probably best to switch it out so youre not shifting up and down all the time. if youre below it enough to not need back and forth shifting, OD on or off makes zero difference. if youre above it enough to not need shifting back and forth, OD on (unless of course pulling a load etc like i said earlier)

rugerm44

I have never had a problem with a toyota auto trans.I take it out when towing or when it kicks in and out going up steep hills.Keep it serviced and put an aux cooler on it.If you tow i would put a trans temp gauge on it.By the time the idiot trans temp light comes on its been over heated for a while! I run mine around town with it on.Never had it get passed 150deg.Its not going to get better mpg with it off.There is about 800 rpm difference with it off.Thats why they put it on there to begin with.

BajaRunner

I have been told, face to face by 2 Toyota mechanics to leave "O/D OFF" whenever driving around town. Put it "ON" highway.

My truck runs better w/ OD OFF anyways. RPMs are too low with it on.

ebelen1

Around here, 35 - 45 mph is normal for street driving, which is what I do a lot of. Since it's mostly street driven, the constant acceleration and braking w/in this mph makes me think keeping the OD off is better for me. Like I said earlier, the truck runs better and the tranny seems to shift smoother w/ the OD off under 45 mph.

Jimmeh

I still don't understand...how would driving with the extra gear turned on be any different then having it turned off at lower speeds? Overdrive is a fancy word for 4th gear isn't it? I can understand having it off while on hills or towing, but still, I don't see the problem of having it on in town or on the highway driving.

Rick F.

Even driving around town, your tranny will occasionaly shift into OD around 40 mph under light load. Turning OD off will prevent that unneccesary shifting. As far as towing and hills, you want to wind up your RPM's a bit more due to the extra load on the engine to take advantage of the extra power and, again, unneccesary shifting. I hate lugging the engine at low RPM's... Makes my skin crawl...

gpcollen1

Either way - i dont think you are going to ruin the tranny...

Does this mean when driving around the city at 20-25 mph we should shift our automatics into 2nd, so we couldnt possible shift into Drive (3rd)???

If you drive enough and actually pay attention, you will notice when your vehicle is shifting back and forth and take it out of OD. Under load, you will do it from the start.

My two cents,
george

surf4runner

i leave it on, because i forget to turn in back on when ive had off.

carose725

if od does nothing except over 40 miles per hr how come if your cruising at about 20-35 miles per hr and hit the od button the rpms change. if it only afects highway driving it should change nothing.

tom_mag

Overdrive is a lower that 1:1 gear ratio and is usually fourth gear. It is usually 0.75:1 ratio so the engine does not have to run high rpms to maintain the speed. I always leave mine on unless I am going up a steep hill with a heavy load or using engine braking on a downhill. If you turn your OD off and on in normal driving you are paranoid. You will always get better mileage in OD so leave it on.

RustBucket

iTrader: (1)

I think there's alot some variance if the torque converter is locked up or not. It's possible that even with OD on, cruising at 30mph, your tranny is actually in 3rd gear, and when you turn the OD off the tranny somehow triggers the converter to unlock a little bit.

I think the bottom line is that if you're lugging the engine when you're in any gear, just freaking downshift it. Auto trannies are stupid, so when you hit a hill and it insists in staying at 1200 rpm help it out and shift down, be it into 3rd, 2nd, or 1st.

As far as fuel economy is concerned, your throttle position has WAY more to do with it than revs. This means that making it up a hill with 1800rpms and 3/4 throttle is much more inefficient than at 3200rpms and 1/4 throttle. I know this from experience since when I regeared from 4.10 to 4.88 my economy went up a little bit, since I'm not into the throttle as much.

rearviewmirror

There's a good chance that the engine will fail before the transmission in a Durango so I am surprised your friend was even remotely concerned about it.

Joshs98Runner

Well Dodge's trucks do have a horrid reputation for tranny failure. I would assume the guy who argued with you has had a problem before and the dealer came up with some bs to blame him for it, resulting in his paranoia...

My last neighbor went out and bought a brand new 1500 Ram in 02 or 03, I warned him of the common tranny failures but he ignored me, he is the type that always has the dealer service his vehicle when it needs fluids and keeps it maintained, even still, 40k miles later his tranny starts taking a crap and all he does is drive it to and from work on business...good thing he bought the extended warranty. I have had many other friends with Ram's have tranny failures, most of them have bought Ford/Chevy after they get tired of it.

bob200587

I know that most auto trannys will shift into OD well before 40 mph if you aren't still accelerating...Like most have said, I prefer to leave automatics out of OD in the city for several reasons:

Less transmission heat
Better fuel economy by helping me keep my foot out of the gas
Better engine braking, and therefore prolonged brake pad and shoe life.

Just to name a few. I also use it when towing or in hilly terrain of course.
Not much reason not to take it out of most yota's as most have the little button on the shifter. I LOVE that thing.