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Explanation of the overdrive button


iain_spen
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Originally posted by carl0s

you answered it in the subject. Kickdown. It causes the box to kick down to the lowest gear it can.

Is that true? Only reason I ask is my auto box will kickdown if I just move the accellerator quickly, I don't need to floor it for it to happen. Unless of course this courses the special Supra 2 gear kick down?
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christ! I started this post and it's doing me head in now.

 

From a bit of experimenting with the O/D i've come to the final conclusion:

 

O/D on - the car feels faster and gets into 4th gear

O/D off - the car doesnt accelerate as fast and can't reach the top speed

 

does this sound about right???... :conf:

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no, it's pretty friggin simple.

 

O/D Off, turns Overdrive off. (honestly, it does)

 

Overdrive is the fourth gear. It's called an overdrive gear because the gear ratio is greater than 1:1. Instead of reducing the gearing, it increases it.

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overdrive is a pain if you're doing around 50mph and are on/off the accelerator. It constantly drops back into overdrive and then back out again. Times like this, you turn overdrive off and it stays in third ready for you to accelerate again.

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Originally posted by iain_spen

it's just feels slower at accelerating when the overdrive is off... may be it's just me lol :p

Are you sure you aren't confusing the Overdrive button with the MANU button? The MANU button will make the car accelerate a lot slower because the car is (pretty much) stuck in 3rd gear.
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  • 1 month later...
Originally posted by Jake

Are you sure you aren't confusing the Overdrive button with the MANU button? The MANU button will make the car accelerate a lot slower because the car is (pretty much) stuck in 3rd gear.

 

It will only be stuck in third if that is where you leave the stick.

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I've found a distinct difference in acceleration rates in any given gear from any given comparable rev range between manual mode and normal mode. My car doesn't seem to go as well sometimes in manual mode. No its not because I am lower down the rev range as I did say comparable revs in comparable gears.

 

If for instance I am accelerating with foot flat to the floor and say approx 4500 rpm lets say in 2nd in manu mode, it feels a touch sluggish. Depress the manu button to reselect normal mode and it will noticeably pick up a lot better. Its only seemed to do this since I fitted my delimiter. I get a flat spot around a ton as well.

 

Could be down to different speed sensors on individual boxes cause differing results.

 

Either way O/D is just an extra gear and has no effect on the rev range of any of the other gears. If you really want to prove it to yourself, go down the road in manu and record the speed that you hit the redline at in 1st 2nd and 3rd. Then doing max accellerate record the the speed you hit the redline at in 1st 2nd and 3rd again. There will be no difference. If you still doubt then also push the O/D button to off and repeat test. O/D won't come on in manu mode.

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  • 2 weeks later...
Guest deepcom

Here's one to consider then -

 

As the O/D doesnt function in manual mode, (yeah you can switch back to auto, automatically get O/D, then switch back to Manual to maintain the O/D until you accelerate sharpish when it switches back to 3rd and then coz your in Manual it stays in 3rd), can you actually get overdrive to come on in manual mode without having to switch back to auto ?

 

Anyone got any ideas about wiring a switch to the auto ECU so that you can manually engage overdrive by pushing an extra button when in manual ? (Would it be possible to wire a switch to the O/D actuator so instead of the auto ECU saying "switch to O/D" you simply have a button you can press ?)

 

And assuming that is possible am I correct is saying that O/D is actually 3rd gear with another cog engaged so you actually get 3rd gear cog + O/D cog engaged simultaneously to give overdrive ? And if so with a manual O/D activation switch would it then be possible to engage the O/D in the other gears as well in effect making the auto box 6 speed ????

 

Your thoughts are appreciated on this one.

 

Andy.

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  • 6 months later...
Guest Rays the roof
Are you sure you aren't confusing the Overdrive button with the MANU button? The MANU button will make the car accelerate a lot slower because the car is (pretty much) stuck in 3rd gear.

 

Not nessa celery true. Fastest 1/4 mile in an NA auto is achieved by starting in Manual with OD light illuminated and gear stick in first, foot to the floor taking it up a gear just before the red line (timing is essential) and then at 78 - 80 flick both Man and OD buttons, again timing is critical. Read all the previous threads in this post agree with some, but not all points. TRY it at Pod and prove your self wrong!!

 

:respekt:

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Not nessa celery true. Fastest 1/4 mile in an NA auto is achieved by starting in Manual with OD light illuminated and gear stick in first, foot to the floor taking it up a gear just before the red line (timing is essential) and then at 78 - 80 flick both Man and OD buttons, again timing is critical. Read all the previous threads in this post agree with some, but not all points. TRY it at Pod and prove your self wrong!!

 

:respekt:

 

he's referring to off-the-line acceleration with the stick left in 'D'. If MANU is enabled while in D, take-off will be slow 'cause the car will skip 1st gear.

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no. we're talking about the one that says "O/D Off" next to it.

 

The red button allows you to pull the J-Specs out of park with the engine off, or something.

 

UK spec doesn't have it.

 

Yep! It's basically for when you breakdown or want to jump start an auto.

 

OR

 

It's an eject button for the passanger seat in an aerotop...that always gets a worried look from the passanger! :eyebrows:

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  • 2 weeks later...
Not nessa celery true. Fastest 1/4 mile in an NA auto is achieved by starting in Manual with OD light illuminated and gear stick in first, foot to the floor taking it up a gear just before the red line (timing is essential) and then at 78 - 80 flick both Man and OD buttons, again timing is critical. Read all the previous threads in this post agree with some, but not all points. TRY it at Pod and prove your self wrong!!
Also worth noting that the NA box handles totally different to the TT. I've owned both and the NA has some of the 'normal' auto box features of changing up gear early and not changing down very quick. I can easily believe the NA needs to be run in manual mode to get a quick time down a strip. The TT is a different matter though.
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