Overdrive On/Off Debate

Hi,
We have a automatic 97 Prado & are having a slight debate on when to use overdrive.

When overdrive is off doing 100klms there is a humming noise which I assumed may be a problem with the gear box.
I've since been told overdrive off for driving around town & towing, then overdrive on for highway driving.
Is this correct?
I thought this didn't apply to older models.

The advice is about right, off means it will hold the revs a little longer, which may help when towing or offroad etc.

I leave od on all the time, it makes little if any difference on the road imo.

The only time i switched OD off was when i towed my Parents caravan. and that was only when id come to a long incline and didnt want to labour anything.

I leave mine on as wobbly said only off for towing or off-road

I'm the same as I leave mine on all the time even when towing my caravan, especially on motorways. Just take it off for long hills or overtaking, etc.

Generally leave it on as above has mentioned. But Kick it off either for engine breaking down long hills, or when towing up long hills. I prefer to let the engine rev higher and spin the water pump quicker, rather than laboring the engine in 4th.

My 2000 Collie doesnt have o/d however, it does have a PWR button, above the 2nd gear start button on the central console, next to gear stick, which holds the gears longer. I presume its because its the pre D4D model with a facelift?

froggy Steve said:

My 2000 Collie doesnt have o/d however, it does have a PWR button, above the 2nd gear start button on the central console, next to gear stick, which holds the gears longer. I presume its because its the pre D4D model with a facelift?

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steve look on the right hand side of the auto shift stick just below the main button to select the mode.
i think your find a nice little round button to select OD on/off

my LC is a pre d4d facelift too.

Well, Fc*k me sideways! I have had that truck 2 and a half years, drive it at least once a week, and never noticed that! God, how embarrassing Actually, it goes to show that it doesnt get cleaned very well inside!
Well, that has made my day, along with cutting the grass for the first time and spending the afternoon snoozing at the lake while dangling some sweetcorn for the fishes

Thank you o great and good ones

Every days a school day Steve

froggy Steve said:

Well, Fc*k me sideways! I have had that truck 2 and a half years, drive it at least once a week, and never noticed that! God, how embarrassing Actually, it goes to show that it doesnt get cleaned very well inside!

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At least you haven't driven around for two years with the O/D off, I will admit it was about six months before I found out about the overdrive button.

tim falce said:

At least you haven't driven around for two years with the O/D off, I will admit it was about six months before I found out about the overdrive button.

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Thats it, I am going to be playing all the time now! O/D on.....O/D off........O/D on.....O/D off..............

Beau said:

Generally leave it on as above has mentioned. But Kick it off either for engine breaking down long hills, or when towing up long hills. I prefer to let the engine rev higher and spin the water pump quicker, rather than laboring the engine in 4th.

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I used the OD button in my 80 the same way, plus if the truck was labouring at all (or I felt the gearing needed to be slightly lower) I would switch it off as well.

Kevin, does your Prado have an ECT (electronic control transmission) button? When this switch is switched on the auto transmission holds the gears for longer, bit like a sport button but not really intended as such in this application. This can also be useful in high load situations, towing, climbing mountain passes etc.

froggy Steve said:

...... it does have a PWR button, above the 2nd gear start button on the central console....

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PWR is the newer version of the ECT button mentioned above, 2nd gear start is a useful feature, I have only seen these on the newer models, D4D and 100 series onwards (don't quote me, this is just my observation).

I found the 2nd gear start very useful on my FZJ105 in Oz, we spent 2.5 hrs climbing out of a valley which hand regular steps formed into the track to force rain water to run off the side and not damage the track. These mounds made an already steep track even steeper at each step! This caused the autobox to kick down to low first as you crested each step, then rev through low first and then changed up into low second to continue climbing. This regular process would soon generate enough heat to cook the auto transmission fluid, so 2nd gear start button was selected and this prevented the autobox from kicking down into first at each crest, saving all the unwanted heat build up and allowed the trick to climb to the top with damaging the auto trans fluid or the gear box.

On my LC's operation of these switches brought up a light on the dash to inform you that they'd be selected, ( IIRC OD displays on the dash when it is off ).

just a little note, with the overdrive on the torque converter will lock up at 50mph but with it off it won't lock up until 60mph in third. So if you coming to a long hill and you think you won't make it all the way above 50 in overdrive then you need to be above 60 in third for it to lock up, once locked up with you foot down it will stay locked up 5mph less than those figures until it releases.
Only an issue if you gearbox is prone to getting hot!

interesting thread guys, makes great reading.

im even more chuffed that ive got a manual.

Rich Sims said:

just a little note, with the overdrive on the torque converter will lock up at 50mph but with it off it won't lock up until 60mph in third. So if you coming to a long hill and you think you won't make it all the way above 50 in overdrive then you need to be above 60 in third for it to lock up, once locked up with you foot down it will stay locked up 5mph less than those figures until it releases.
Only an issue if you gearbox is prone to getting hot!

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Does the lock up depend on how hard the truck is accelerating? because on mine it locks up at 40mph (overdrive selected) and 50mph (overdrive off)

How can you tell when the OD has locked?

On my LC i feel it when the revs drop around 55mph(indicated) to about 1.8k revs and then it just wants to pull and Pull

wobbly said:

How can you tell when the OD has locked?

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It gives a little sort of lurch, very slight, almost like it's found another gear, well that's how I look at it anyway.

wobbly said:

How can you tell when the OD has locked?

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It's the torque converter that locks up, the OD is selected via the button and engages immediately when the button is operated. The torque converter locks up as discribed by Chas and Silvercruiser above.