Automatic tranny - anyone use overdrive ?

I have 99 auto 4 cyl. Deos anyone use overdrive? I always have it on. When and I suppose to use it and how does it work? Also what is ECT button on the dash ? Thanks

 

Ur transmission will always use overdrive in high speed low load situations (cruising on the freeway) unless u turn O/D off... All overdrive is, is a gear ratio higher than 1:1 meaning ur wheels are spinning faster than the engine. The main purpose of overdrive is less wear on the engine and better mpg. Leave it on and let ur trans decide when it's necessary to downshift. That's what an auto trans is for! As far as the ect button idk what it is...

 

as Styx said, leave it on if you cruise the highway, it's 4th gear so the rpms are lower. I usually turn mine off when going less than 45 mph (~2k rpms) so the trans doesn't gear hunt during my commute. If I hit 42ish and know I'll be going faster I turn it on and let it upshift to run easier

the ECT button was something I had to look up years ago when trying to explain to my grandfather (he had an '03 4cyl auto TRD OR). When the ECT button is ON it theoretically should "hold" the upshifting of the trans longer to get more out of the gear. So in essence it will hold onto 1st, 2nd, and 3rd longer before moving to the next gear. What algorithm is used I have no clue and have not noticed "much" of a difference with it on or off

 

Here is a basic explanation from Toyota . Covers most of their models
http://www.autoshop101.com/forms/h16.pdf

 

ECT Power generally shifts 2,3,4 normally if you drive normal. The biggest difference is the lock up clutch. With ECT Normal your trans wants to lock up at 50mph and with power, the target speed is 60 mph.

If you drive a little harder or have a load on the engine (ie towing/hauling), ECT Normal will still bias your shifts to be early. Power won't and will bias them to hold as stated above.

As far as OD, if you are towing/hauling something very heavy, run with it off. With the OD off, your trans will engage the lockup clutch in 3rd gear, with its target speed at 50mph (im not sure if ECT Power changes this).

 

That's a great Link! Thanks for posting it.

 

OD is 4th gear.

 

The ECT switch changes the shift points , best used when towing, I'd keep O/D off unless on freeway or speeds in excess of 50-55

 

thanks all for the replies!

I usually drive with OD on whether on street or freeway. The car seems to run smoother and I also seem to get better gas mileage. Is it bad to always drive with it OD on? In my old camry, i probably drove with OD on the few years I owned it. Will I damage my tranny or lessen its life or engine life driving with OD always on? Thanks again guys

 

not at all, it's designed to be on for normal driving for that reason. technically they could have left out the button and eliminated the choice to have it on/off but Toyota saw fit to let us choose. plus being a truck and towing a button is easier to press than shifting the stick back and forth, more time with hands on the wheel.

 

^ This. Basically the button is not there to choose to have it "on" but rather to choose to have it "off."

Keep it on unless you are towing/hauling something heavy.

 

Newbie here... I know this is an old thread and just need some input. I recently got a 2003 Tacoma 2wd 2.4 with auto.

I live in Western NC with LOTS of hills. I do have the OD button and I’ve been using it for big long hills as the engine struggles with OD on with no load nor towing. People here usually are impatient when you slow down going up these grades! I usually keep my speed at 60 mph once I hit it. Tach at around 3000 rpms+ and I usually turn OD once I reach top. My question is what speed range is safe for OD off for A44D transmission?

 

not really a question of "speed" range as "rpm" range. sustained high spinning will heat up the trans fluid, which is why gear hunting is bad (spin up, then down, and repeat). but they are also designed to handle what the engine can put out, 3k rpm I wouldn't worry about. I wouldn't run 4500 all day but generally speaking I do what you do going up hills, take O/D off and wait until I get to a more level spot to turn it back on.

 

There's no real reason to turn the o/d off unless you're going up a hill or towing something and the trany is hunting for gears.

An auto trans will pick the right gear for what it needs (generally), but if you're going up a hill and it's constantly shifting back and forth, I'd just take the o/d off and keep it off until the top of the hill.

 

Dear ZerO,

Hopefully, when you named yourself, you did not name yourself by how much IQ you have. LOL

Okay, so you want to know about how an overdrive works in an automatic transmission. I am hoping your Tacoma has a tachometer because that will make understanding this a lot easier. Automatic transmissions in the last thirty years have come equipped from the factory with an overdrive. In the last five years, automatic transmissions come equipped with many gears and a vast supply of intelligence so they make driving them extremely efficient and easy. Prior to about 1985, automatic transmissions were primarily three speed sequential transmissions. This in turn meant that they would rev at a high RPM after about 60 miles per hour on the freeway because their final third gear was a 1:1 gear, and they had no way of upshifting to another gear to change the revolutions of the engine. As a result, these old three speed automatic transmissions were not very fuel efficient. Good examples of old three speed automatics are the Chevy Turbo 350 an Turbo 400 transmissions.

Your old Tacoma is equipped with a four speed automatic transmission in which the fourth or the final gear is an overdrive. The best way to observe how this works is to drive it down the freeway with the overdrive turned off at a consistent 60 miles per hour and record what your RPMs are on your tachometer. Then do the same test with the overdrive turned on. You will notice about a 500 to 600 revolutions per minute difference between having the overdrive turned on compared to it being off. With the overdrive on, the revolutions of your engine will be reduced from it being turned off. As a result, your engine is revolving less so it is using less fuel.

Hope that helps,
Paul

 

Thanks for all your responses!