isn't that pretty redundant? i always wanted to know the difference. i know some of the bmw, audi's, vw's, and jag's have 6 speed autos, is that 6 speed with overdrive, and the some mercedes have 7 speed autos. just curious.

our cars have a 3 speed auto with overdrive :-\ but why do some people say 4 speed auto.

technicaly overdrive is suppose to make the out put shaft of the a/t spin faster than the input shaft. this is ment for high way cruising. the final gear in any a/t pretty much does the same thing. my guess on the reason they call it over drive is because you can turn it on and off.

but why do 5 speed auto's yeild a better 0-60 time or better performance than a 4 speed auto w/ overdrive. like the camry with the v6 had a 4 speed auto with overdrive. they then changed to a 5 speed auto. and the 0-60 times was like .5-.8 seconds faster!

Originally posted by TheWoo
but why do 5 speed auto's yeild a better 0-60 time or better performance than a 4 speed auto w/ overdrive. like the camry with the v6 had a 4 speed auto with overdrive. they then changed to a 5 speed auto. and the 0-60 times was like .5-.8 seconds faster!


They don't necessarily yield better 0-60 times, lots of other factors going on there - they COULD have used different gear ratios, different torque converters, they could have remapped fuel or spark advance, etc...

5 speed auto and 4 speed auto w/OD are essentially the same thing, in this case. The five speed auto in the newer camrys is still a 4 speed with overdrive... the OD part is just a reference to the fact that the last gear is overdriven (numerically less than 1:1 or as stated previously, the output shaft is spinning faster than the input shaft).

5= shorter gears, you go through gears faster when theyre shorter from experience

4 Speed Auto "With Overdrive" is what we have. It just means that 4th gear is less than a 1:1 ratio, therefore meaning that the shaft out of the transmission is spinning faster than the one in, as Stealth said.

The reason the five speed automatic has a faster 0 to 60 time is because the gears are shorter and it gets into the powerband a lot faster. Thats a large part of why a stick is much faster than an auto is because it has shorter gears, and so it gets into the powerband much much faster. If we had engines with serious torque the difference wouldn't be as noticable, but on top-end high revving four cylinders, the gearing matters a whole lot because you need to get into the powerband asap.

i think i get it thanks people! so what is overdrive for should i turn it off when crusing through the city or should i just leave it on.

Depends. If you turn it off, your engine will probably hang at ~3000 RPMs all the time at 45 mph, and that'll give you great throttle response because that's really where the engine starts to pick up, at least on my auto.

However, it will hurt your gas mileage a good bit, and because of that I keep mine off all the time. If I really need to get going, I can just put my foot in it. Also, the claim could be made that keeping it off puts more wear on the engine because the engine will be working a lot more just to keep up to speed, and it will have more wear and tear on the drivetrain.

If you're going up a hill or towing something, the O/D off switch will only come in hand to prevent the transmission from constantly switching back and forth between 3rd and 4th gear, which can become very annoying. Otherwise, you shouldn't even notice it.;)

I personally can't see any real benefit or performance advantage to a 5A or 6A over a 4A.....(smoother shifting perhaps?)........:-\

onyl time i take o/d off is on the highway. if your between the speeds of 40-70mph dropping the tranny into 3rd gear from 4th (or taking the overdrive of when it was on) and then slamming the gas gives the car a nice boot, she should redline for a few seconds and then reset to about 5k.

other than that o/d is useless

Originally posted by Xard
4 Speed Auto "With Overdrive" is what we have. It just means that 4th gear is less than a 1:1 ratio, therefore meaning that the shaft out of the transmission is spinning faster than the one in, as Stealth said.

The reason the five speed automatic has a faster 0 to 60 time is because the gears are shorter and it gets into the powerband a lot faster. Thats a large part of why a stick is much faster than an auto is because it has shorter gears, and so it gets into the powerband much much faster. If we had engines with serious torque the difference wouldn't be as noticable, but on top-end high revving four cylinders, the gearing matters a whole lot because you need to get into the powerband asap.


But I'll still bet money that the 5 speed auto in the Camry he speaks of still has an overdriven 5th gear.... meaning it is exactly the same as a 4 speed auto w/OD.

It's a pity the CVT is such a slug....and it's also a shame that Nissan doesn't have a 5A that can swap into the P10/P11.

First, the Camry has FIVE speeds, that's why it isn't a FOUR speed automatic with Overdrive. If the final gear was a 1:1 gear, then it would be a five speed automatic with no overdrive. The final gear is < 1:1, so it is a five speed automatic with overdrive. Same for our cars. We have a four speed automatic, with overdrive. 3rd is 1:1, 4th (or, overdrive "on") is < 1:1. If you need another example, here's the carpoint page for the aforementioned Camry: "http://autos.msn.com/research/vip/overview.aspx?modelid=10922&src=vip" Note, it has a four speed auto with overdrive, a five speed auto with overdrive, and a five speed manual, again with overdrive. Does this mean that it has a 5 gear, 6 gear, and 6 gear? No. I don't see how this is so difficult.

As for why it's faster: As we've said before, the shorter gearing helps immensely, especially on a car without a lot of low-end torque. With the shorter gearing, instead of having to wait for the car to get to 20 mph to get into the powerband, it gets into the powerband at 10 or 15 mph. This means that you get into power sooner, acceleration happens faster afterwards, and, more often, you're more likely to -stay- in the powerband after you shift up. Ie, on the five speed, when you shift up you might drop from 7000 rpms to 4000 rpms. On the four speed, you drop to 3500 or 3000 rpms. This difference can mean a lot, especially on very top-end heavy cars, where you need to keep your RPMs as high as possible so that you still make power.

Originally posted by Xard
First, the Camry has FIVE speeds, that's why it isn't a FOUR speed automatic with Overdrive. If the final gear was a 1:1 gear, then it would be a five speed automatic with no overdrive. The final gear is &lt; 1:1, so it is a five speed automatic with overdrive. Same for our cars. We have a four speed automatic, with overdrive. 3rd is 1:1, 4th (or, overdrive &quot;on&quot;) is &lt; 1:1. If you need another example, here's the carpoint page for the aforementioned Camry: &quot;http://autos.msn.com/research/vip/overview.aspx?modelid=10922&amp;src=vip &quot; Note, it has a four speed auto with overdrive, a five speed auto with overdrive, and a five speed manual, again with overdrive. Does this mean that it has a 5 gear, 6 gear, and 6 gear? No. I don't see how this is so difficult.



It's not difficult, the car has 5 speeds total, the 5th gear being overdrive. It is NOT a 5 speed with another overdrive gear. Look it up, the 5th gear is numerically less than 1:1.

Could be 0.8:1 or something like that.

That's exactly what I'm saying, however, saying that it "has overdrive" just means the FINAL gear has a ratio of < 1:1. Not that it has ANOTHER speed with a overdriven ratio. Another case in point, the P10: http://autos.msn.com/research/vip/overview.aspx?modelid=1411&src=vip
Look, 4 Speed Automatic with Overdrive. It has four gears, the last gear (4th) is overdriven. ratio likely around .8:1, like you said.
The Camry has a 5 Speed Automatic with overdrive. It has five gears, and the last one is overdriven.
The overdriven gear counts as a speed.

Originally posted by Xard
That's exactly what I'm saying, however, saying that it &quot;has overdrive&quot; just means the FINAL gear has a ratio of &lt; 1:1. Not that it has ANOTHER speed with a overdriven ratio. Another case in point, the P10: http://autos.msn.com/research/vip/overview.aspx?modelid=1411&amp;src=vip
Look, 4 Speed Automatic with Overdrive. It has four gears, the last gear (4th) is overdriven. ratio likely around .8:1, like you said.
The Camry has a 5 Speed Automatic with overdrive. It has five gears, and the last one is overdriven.
The overdriven gear counts as a speed.


Yeah, good, we're on the same page... miscommunication is a bitch. I thought you were trying to say that the Camry had 5 speeds AND a sixth overdrive gear. Oh well, no harm done. Let this be a lesson to you all: don't drink and post.