Overdrive, Is It an Additional Speed Gear?

It's a 5th gear.

Overdrive has got to be one of the most misused (mostly by marketing!!) terms around.

The common definition for overdrive is that it is any gear ratio that results in the output speed of the transmission being higher than the input speed. As an example, many semi trucks have multiple overdrive gears.

It would normally be included in the listed gears, so if you say that you have a 4 speed it should be 4 total unless indicated as 4 plus overdrive.

I have to agree with Lynn this time. An overdrive is a gear or gearbox that can be supplementary used according the car's parameters. The driver or a automatic device can switch it on or off. I remember the old jaguar XJ .. class that had a small switch on top of the gear handle permitting to use the overdrive. It only worked in 5th gear and gave a supplementary ratio of 1:1.14 to bring the RPM down for the same speed.

It is a small gearbox that definitely is only made for the high gears. It is small and under sized for the first gears. I found that out by shortening the 5th gear contact to it.

Using the overdrive in first and second just destroyed the gearbox, because it was not designed for these higher couples.

Most of the time it is an option to a regular gear box and when not part of the original gear box it requires a shorter rear end drive shaft.

I think you're referring to an overdrive unit, or splitter- something my mother had on an old Ford Clubwagon. These are supplementary transmissions that give you combination ratios eg. 2x3 speed. Am I correct on that?

They mostly come on stick shift gearboxes. Had one on the Jag XJ 6 and also on my Porsche. The ratio is not that big: it is actually meant to use on high ways at high speed (in the good old days) to reduce the RPM's of the engine for the same speed, saving some gas with bringing the set up to run at a more economic spot on the engine performance curve.

The overdrive had planetary gears in it and was placed in line with the transmission.

It was activated by a solenoid.

However, the system can also work on automatic gearboxes, if adopted.

I thought that's what you meant. As far as I know, in modern (1990 and newer) light vehicles that come from the factory with overdrive it's always just another gear in the transmission and not an add-on. Could be wrong though!

Thank you both for taking time to answer my question. I am actually having an issue with my car. Can you please have a look at my question at the link below? I still need help.

http://www.clublexus.com/forums/es300-and-es330/703943-p0773-on-2001-es300-location-of-the-solenoid.html

Thank you again!

I went to the other site: http://www.clublexus.com/forums/es300-and-es330/703943-p0773-on-2001-es300-location-of-the-solenoid.html

msekanha is probably correct about the solenoid being inside the transmission, but I don't know for sure. If you have the service manual, does it include transmission maintenance? There is probably a wiring harness between the transmission control computer/module and the transmission. Your problem could be there, outside the transmission.

Regarding the number of gears, in current cars, I think the advertised number of gears includes overdrive(s). After all, the manufacturers want to advertise as high a number as possible - more is better, right? My '03 Ford Explorer has a 5 speed automatic, and I think the top 2 are overdrives. But the overdrive button only locks out the top gear.

There is another issue though that msekanha has apparently misled you on. That is torque converter lock-up. The code you are getting, P0773, relates to that. Inside modern (last 25 - 30 years?) torque converters there is a hydraulically operated clutch that eliminates the 'fluid slippage' when activated by the transmission control computer. This increases mileage and decreases the heat that the transmission fluid has to eliminate. If you accelerate from a stop on a smooth, level road, you may be able to feel (and see on the tachometer) when the torque converter locks up - if feels like another shift and the RPM's drop. Most, if not all, control systems only allow the torque converter to lock-up in the highest gear.

You may get better info if you determine which transmission you have and post to a Toyota or Lexus specific forum.

Thank you very much for reading my question.

That's what has confused me. If that shift solenoid is what enables my transmission to enter over drive, I would have been having an issue with my O/D Led, i.e; I wouldn't be able to turn it ON or OFF.

I believe this solenoid 'Shift Solenoid E' has got nothing to do with O/D, since I am still able to turn it ON and OFF.

Also, I can notice the gears change while I am driving and I can count upto four Engine Rev Drops - so, I was wondering if it is the 5th Gear that is not getting activated since I have a problem with this solenoid.

Thank you again.

Start off in 1st gear.

1st to 2nd: One gear change (rpm drop)

2 to 3: two gear changes (rpm drop)

3-4: three gear changes (rpm drop)

4-5: four gear changes. (rpm drop)

Yep it's a 5 speed.

Or a 4 speed with lock-up torque converter.

Then it's time to look for loose wires, damaged solenoid and/or a blown fuse.

A lock-up torque converter has no effect on any gear ratios and cannot be considered a "speed".

There may, or may not, be a discernible RPM change when it does lock up.

The Toyota U250E transmission, available in 2001-2006 V6 cars only, is listed as a 5 speed, with 4th and 5th both being over 1:1.

The U140E and U240E transmissions (4 cyl engines) are both 4 speed.

[edit] Post your other question here at CR4. Some of us don't have time to crawl all over the interweb looking for stuff.

^{Did I really say that out loud?}

Thank you very much, Door Man. I will post that as a new question.

Now you've done it.

"It's a 4-Speed car with an option for Over-drive"

Today it's not an option. In the past it was. Was the option chosen and does the car have overdrive?

Yes. It has got a seperate 'over drive' switch and can be turned off and on, the only thing I am not sure about is whether the over-drive will go beyond the 4th Gear or the 4th gear itself is included in the over-drive.

Appears to have a Toyota U140E transmission here is a link to the gears of all U models

http://en.wikipedia.org/wiki/Toyota_U_transmission

Over drive is a separate gear.

Autobroker,

You've "earned your keep today".

Nice work.

"If you accelerate from a stop on a smooth, level road, you may be able to feel (and see on the tachometer) when the torque converter locks up - if feels like another shift and the RPM's drop. Most, if not all, control systems only allow the torque converter to lock-up in the highest gear."

I have a PCS controller that runs a Ford E4OD automatic transmission and that had the option for TC lockup in all gears. I used a higher than stock stall rated torque converter so that when loaded down the TC lockup split each of the 4 gears giving it a very realistic 8 speed automatic feel!

Ah but if you are a software designer you'll start counting gears at zero.
maybe it's not a gear, maybe it's implemented with rubbver bands, cones or small particles of anti matter or black holes that disprupt the space time continuum in the vicinity of the car.

Nah, it's all done with gears... so it's a gear.
Or is it done with mirrors...?
Del

The term "overdrive" is being used ambiguously here, and possibly incorrectly. The most correct usage would be as an overrunning clutch, which has not been mentioned yet. A supplemental gear, such as the higher speed lower torque item already described, is also correct usage. Torque converter lockup is not really overdrive, but may be called that incorrectly.

Yes, overdrive is an additional gear, generally for highway cruising.

Does it mean that the 4th gear itself is the Over Drive?

Yes, RAMConsult, so much confusion for such a simple subject. Wikipedia actually clarifies much to those that are open, and is spurned by those that are closed. Too much missing from this post!

This is Wikipedia's first paragraph on 'overdrive': "An overdrive (OD) is a mechanism that allows an automobile to cruise at sustained speed with reduced engine RPM, leading to better fuel economy, lower noise, and lower wear.^[1]" Is this gibberish, or is this what we have all been saying all along?

I am still trying to find out why they still fit those quaint little O/D switches on so many gear sticks in the US, like they used to do in Europe in the old days, so many years ago. But nobody seems to be able to help me, not even the great Wikipedia!

You still insist upon irrelevant rants and lies rather than addressing the issues in question, even to the point of refusing to answer some very basic and simple questions that are the crux of the biscuit:

· Why do some people use the term 'overdrive', whilst others don't, for transmissions that are essentially identical, or do the same thing with the same number of gears and the same gear ratios?

· Why is it apparently offered as something extra, or something 'better', when it has in fact been universally available as standard equipment in the US for more than 30 years, and in Europe for more than 40-50 years?

· Why is the term used in the US but not in Europe?

· You said: "In the US (since the 80's), the automakers use the term all the time"; so why do so many people not know what it is, what it does or how to use it?

Having seen what I have seen from you on this thread, I am not surprised that you cannot answer these, and that you work in the auto business.

Do you not agree that the gearbox ratio is rather meaningless when final-drive ratio and wheel size are not considered? Wouldn't engine revs vs driveshaft revs, or even engine revs vs road speed be more meaningful? If so, which point would equate with the 'magical' 1:1 gearbox ratio that denotes overdrive? If more meaningful terms had been used from the start, the term 'overdrive' would never have been used in the first place. This might have avoided much confusion and misunderstanding.

Just food for thought here. Back when almost all automobiles had the transmission bolted directly to the back of the engine, and the power consumed by a transmission was at its lowest point when in direct, an "overdrive" was easy to understand as a method of allowing the engine to loaf at lower speeds while the automobile was just cruising at highway speeds. But don't forget that most often, equipping a car with an overdrive from the factory it would come with a numerically higher rear axle ratio to compensate some for the loss of power in overdrive.

As for a more meaningful term, well, as far back as 1992, Motor Trend would list both axle ratio, and final drive ratio. Also listed, was a defining specification;

"Engine rpm @60 mph in top gear".

Yes, you are right. And I think I already mentioned that some European manufacturers list in their specs "Road Speed @ 1000rpm". This, along with "MPG" is far more useful and meaningful than just calling something an 'overdrive' transmission, and saying it is better.

Try this link that lists Lexus gear ratios:

http://www.clublexus.com/forums/es300-and-es330/263547-gear-ratios-for-the-92-93-es300.html

It also lists the final drive ratios.

Took about 1 minute on google to find.(sigh)

Is your Check Engine Light or MIL on?On your Lexus there is a built in function when there are codes that cause the light to go on.And the function is the transmission will not shift into OD.If your light is not on and it won't shift into OD,it might be a stuck solenoid,a corroded connector on the trans.,the brake cancel switch,to name a few things.

Hi, I'm in the industry and I've sold a lot of Lexus ES 300's. The transmission has four forward gears which includes an overdrive plus a reverse gear (total of 5). All 2001 Lexus ES 300's came with the same transmission, which is also the same unit used in the Toyota Camry V-6 and Toyota Avalon.

One of the problems with we engineers is that we overthink things and are too logical. Some of the responses in this post are logical, but are incorrect. The logic being that in the distant past, cars had an external overdrive unit, which would give an additional "highway" gear. The fact is that a three speed (forward gears) with an external overdrive actually becomes a six speed, because you could use the overdrive in all gears - theoretically. In reality, the overdrive is not designed to take a lot of stress and using it in the first two gears may damage the unit.

Hello Autobroker! I am very glad to see your replies :)

Today, I had a long trip and I reset the battery to clear the MIL. Then about driving for an hour, the MIL kept OFF and I drove at 60MPH max.

On the way back, the MIL came on again. Last time I had it checked, it threw the code P0773 : P0773 Shift Solenoid "E" (Lock-Up Solenoid) Electrical Circuit Malfunction .

One thing is for sure, that it is not affecting the O/D, as suggested by some people (on another forum).

I just want to say thank you for sharing your knowledge and helping me.

Thank you very much everyone for taking time and sharing your experience, I am really very happy to see all the replies.

Just an update : I had a long drive today and I tried switching off the O/D switch while the car was at the speed of 60MPH, the Engine turned faster and I could notice the difference and then it went normal as soon as I turned it back ON.

So, one thing I am sure about is that this solenoid has got nothing to do with the O/D and my O/D is still working fine.

I have checked the fluid today and there was not sign of burning. Why the car keeps running for some hundred miles with not MIL ON and then again it gives the MIL ON.

Shouldn't it turn ON as soon as the Solenoid is supposed to be energized and it returns the fault?

Why I don't see any difference in driving if the torque convertor has a problem?

Thank you for your time.

Thank you very much for the detailed reply.

I can see now the Engine Rev 2.2 to 2.3 X 1000 RPM @ speed of 60 MPH. I expect it to go lower than this after I manage to get it solved.

There is so much misunderstanding about overdrive.

Lyn is totally correct (and Autobroker is also correct), in terms of the Lexus ES300 it means a 5^th gear, which is what we have all had in Europe with manual transmissions since the early 80s, and subsequently with automatics.

Overdrive was introduced by British Auto manufacturers in the 60s when the Brits gained 'Motorways' that enabled them to maintain constant speeds over sustained periods of time at sustained high (relative!) speeds. Overdrive enabled them to maintain higher speeds at lower revs, for better fuel consumption. Initially it was always a unit that was external to the existing (usually) 4-speed gearbox that reduced the overall gear ratio. It was sometimes understood that the overall 'overdrive' ratio was less than 1.00:1, hence the term 'overdrive'. On most British cars at the time it was usable only on 3^rd and 4^th gears (sometimes only on 4^th, but making it effectively a 5 or 6 speed gearbox), thus for high-speed motorway ('highway') usage only, and was usually activated by a switch on the gear lever itself. It disappeared in the UK with the advent of 5-speed and 6-speed gearboxes from the early 80s onwards (where the 5^th+ gears were 'overdrive' anyway, in terms of a less than 1:1 overall ratio. In the 60s,the Mini had a 1:1 4^th gear ratio, due to its' small wheel diameter, but most cars were more than 1:1, although my VW Beetle is 0.89:1 in 4th).

There have been a few manufacturers since the early 80s that have used the term 'overdrive' to promise something special, (eg., in one case, extra power at high speed? !!!), but it is always quite meaningless. I am surprised that Lexus have been prepared to risk the assumption that their customers will be totally bamboozled by terminology. It's a 5 speed gearbox... apparently with some problems on 5th!

All manufacturers call transmissions like this "overdrive"

No they don't, and that is my point. As I said, my VW Beetle has a 4th gear ratio of 0.89:1, but it has never been called 'Overdrive'. Every car I have ever owned has had a 5th (or 6th) gear ratio of less than 1:1, but none of them were ever called 'overdrive'. I don't know of any transmissions these days that don't have a top gear ratio of less than 1:1, but until now I have never heard any manufacturer refer to their top gear as 'overdrive'. So why do Lexus choose to do so? It implies that something is different (or better!) than what everyone else does, when in fact it is different only in name.

There is some disagreement on terms here. I have always herd of a transmission ratio that was lower than 1:1 as an overdrive. With the advent of front wheel drive transmissions that also incorporate a "final drive" ratio into the transmission assembly, there are bound to some new ground, and some blurring of common terms.

As for overdrives coming out in the sixties, I must disagree. I inherited a 57 Ford with a 312 V8 and a three speed column mounted shifter. It had 4.11 rear end, with factory installed overdrive. It was cable activated, and the unit was installed in place of the normal tail shaft of the Ford 3 speed tranny.

Lock up torque converters can be programmed to work in any gear. The HT series from Allison has some transmissions lock up the converter in 2 through 5 . My particular design is a second gear start (unless manually selecting 1st). The shift sequence is 2 converter, 2 lockup, 3 converter, 3 lockup, 4 converter, 4 lockup, 5 converter, 5 lockup.

You are right, but there always has been some disagreement on terms. I am now wondering if the "less than 1:1 ratio" is actually an American thing. Thinking about it, I have never seen it called overdrive in Europe unless it referred to a separately activated unit, but most, if not all, European manual transmissions since the 50s/60s have had a top-gear ratio of less than 1:1. So by this definition they are 'overdrive' transmissions, but they have never been called that. You are quite right to highlight the advent of front wheel drive transmissions, but in Europe, at least, this meant the term disappeared because overdrives (in the old sense) disappeared. It was not possible to fit the usual separate overdrives on a front wheel drive arrangement (they had been fitted, as in the US, between the gearbox and the driveshaft on rear wheel drive cars), and it was not necessary as top gears were becoming 'longer', and 5-speeds were being introduced. (On all the front-drive cars I know, the final drive is still a separate unit, even if it is located in the transmission housing, and my manuals quote the final drive ratio separately to the gear ratios).

You are also right about dates, and I was very imprecise. What I meant to say was that overdrives became very prevalent on British cars in the 60s (when volume manufacturers such as Triumph, Sunbeam, etc. started fitting it on many of their sports cars). In fact, the first production units in the UK arrived in 1948, and people like Aston Martin were certainly using them in the 50s. It is quite possible that the fact that overdrives in Europe at this time were used mostly on high-performance sports cars actually gave rise to the misapprehension that overdrive improves power or performance, when in fact it just allowed them to maintain 'short' gearing for sports driving whilst providing 'long' gearing for cruising.

I believe that overdrives were quite common in the US in the 50s on manual transmissions, and can still be had from Gear Vendors, Inc. They bought the rights to the original UK supplier, GKN Laycock (originally Laycock de Normanville - what a lovely name for a humble overdrive!), and the few others have long since disappeared.

The first transmission here that I remember being "converted" to an overdrive was the Ford Top cover four speed manual transmission. They left fourth gear 1:1, but changed third gear to something less than 1:1. Then to keep a normal shifting pattern, they inverted the shift arm for third/fourth. This allowed normal gear sequences, while maintaining a normal shift pattern. It just looked strange from below the floor.

So, would that Ford transmission be a three speed with overdrive, or a four speed transmission?

Now that is an interesting one, and a very good question. Surely it should be 'three speed plus overdrive', or 'four speed with overdrive', or just 'four speed'? I would be inclined to go for the latter, but I guess it all depends on which overdrive definition you use, and on which side of the pond you are.

I think that much of the confusion and misunderstanding is down to the hype put out by US auto manufacturers when the fuel crisis in the 70s forced them to take fuel economy and emissions more seriously, and to do a proper job of gear ratio selection. Hence the birth of the AOD units, which should really have been developed many years earlier. It is interesting that non-US manufacturers, such as Lexus and Audi, will sell a particular vehicle in the US with an 'overdrive' transmission, but the same vehicle in Europe (with the same transmission) will have a 5-speed or 6-speed, but not overdrive.

Yes, it's the new improved version of marketing and profit-making

Indeed. It is amazing what marketing people can do with an emotive word with ultra-positive connotations. If the marketing people at VW (that's a good question, do they have marketing people at VW?) had had their wits about them, they would have called the fourth gear in my Beetle an overdrive, then we would all feel like we were really driving Porsches, and they would have sold millions of them!

Early versions of the THM 400 had variable pitch torque converters. In effect a two speed torqu converter. There were companies that sold kits to convert them to a driver controlled switch. The original design was a switch mounted to the gas pedel. WOT caused downshift, as well as high slip in the converter. If held long enough, the trans would automaticly upshift, but the converter would stay in high slip. One needed to back off of the throttle just a hair, to take it out of high slip. By that time, speeds were well over 100 as the 400 was only in high powered cars.

I am referring to the usage of the term 'overdrive' rather than the definition being an American thing. Why do US auto manufacturers feel the need to use the term, when European auto manufacturers only have to use it for the US market, but not for Europeans? Judging by the total confusion and lack of understang that I keep coming across, it's not even as if they have done much of a job explaining to US car buyers what overdrive is, or what it means in practical terms. No one seems to know. It just seems to be something offered by auto manufacturers that is new, special, better, desirable, that makes your car better, whatever it is that it actually does. But in Europe it is an irrelevant term. Nobody is really interested in gear ratios being more or less than 1:1, as long as they have suitable ratios for everyday driving. It is something that is expected in Europe anyway, and has been supplied for many years without the need for special buttons or lights.

I can't believe this! Nobody has said that overdrive exists only in the US, only that these days it is more prevalent there. (Please read what I've posted before!!!) It seems you might have found a few exceptions that prove the rule, although no one has said that overdrive doesn't exist outside the US. I would be interested to see where Tata mention the use of overdrive. They don't even have an automatic transmission yet. Even their top-of-the range Manza only has a "5 speed manual gearbox".

I can't believe what you say about "stress the overdrive gear and break it."!!!!!?????". This is so ridiculous it beggars belief!. If Renault had ever told me not to use 5^th gear for risk of breaking it I might never have bought my car! (There were plenty enough other reasons not to buy it!. Can you really believe anybody buying a car where the gearbox is so underdesigned that it will not handle the vehicles' normal power output? It beggars belief! This is a downright stupid idea for having an overdrive override!! Don't waste your time asking if any of our European cousins have overdrive, just ask them if they would actually buy a car where top gear could fail if they do not disable it. I could tell you the answer now if you like!

I'm not going to waste much more time on this. You can't even get my name right, no wonder you can't be bothered to read or understand what I have actually written, or do you just choose to twist it on purpose (or is that giving you too much credit)? Would it help you understand if I write more slowly?

"Post 68:…" I never actually wrote that "it is an American thing", and if you read my very first post you will notice that I was talking even then about overdrive in the UK (outside of the US, I believe), and you will note that I have also talked about Volvo of Sweden (outside the US, I believe) so you don't need to 'simply' show me that the term is used in many places outside the US. We all know that already. It is obvious, and if you look carefully you will see that I have never denied it.

But I have been saying that 'overdrive' is currently more prevalent (that means more common) in the US than anywhere else, and particularly than Europe. In fact, it is currently quite rare outside of the US, despite what you seem to think. You seem to insist that I am wrong, so if you are telling me that it is just as common (or even almost) then why don't you dig up some figures showing manufacturers, models and production volumes of cars with 'overdrive' (especially 'automatic with overdrive' outside the US. What you have dug up so far does nothing to prove your case. Have you not noticed that manufacturers like Lexus, Audi, BMW and Porsche have used 'overdrive' for their cars for the US market, but never in Europe?

"Tata Nano…." Your feeble googling efforts indicate that you are too ready to take things at face value, and completely incapable of interpreting what you see, which makes the results totally meaningless (none of your links really prove anything, if you look at them carefully). Have another (closer) look at your "Tata Nano" link, and you will see that they are promising the automatic CVT transmission to come. They have been promising this for at least 5 years, and you will see it promised on many websites, but in fact it has never been produced. IT DOES NOT EXIST. I don't know where you got that photo from, but it is certainly not a Tata. If you look at the specifications and brochures on Tata's own website (http://www.tatamotors.com/) you will see that there are no automatic transmissions on any of their cars. You are not very good at this, are you?

My Renault has a 5-speed automatic transmission. I don't call the 5^th gear overdrive, and neither do Renault. But I do know that the gearbox is designed to handle more than the max towing weight (more than 2 tons) in addition to the cars' max laden weight (also more than 2 tons) plus safety margin, without problems. Being an automatic, it is designed to select the most appropriate gear for the conditions automatically. Renaults are far from perfect, but I have never heard of gearbox problems with them.

No, I am not trying to win anything. And, as you have seen, I am quite happy to admit it when I am wrong. But "willing to lie"? You accuse me of saying "it is an American thing", and have gone to ridiculous lengths to try to disprove this, whilst continuing the accusations. What I actually said in post#58 was "I am now wondering if the "less than 1:1 ratio" is actually an American thing." Now I can understand when you miss the beautiful subtleties of the English language, but in this case it is not subtle; the difference between "it is…" and "I am now wondering if…" is huge, absolutely enormous. The former is a statement (often supposedly of fact), whilst the latter is of a quizzical nature, inviting informative responses (although nonsense and crass stupidity is sometimes to be expected!). Regarding post #68, I think it is too clear and obvious to repeat. If it defeats you, tell me which word you are struggling with. You accuse me of knowing nothing of the US auto industry, when in fact I have good knowledge since 1959 (OK, actually that is pushing it a bit, I was only a year old, and, to be honest, I remember nothing of the trip from Alberta, via Montana and all the northern states to Nova Scotia, but I do remember the times since 1968, and actually driving in Canada and the US from 1977 onwards, and buying and owning and driving cars since then. Tell me of your experience outside the US!! (I have covered 100s of thousands of miles in 100s of different cars on many continents).

Regarding your second point, I am not comparing my Renault with a Ford F150 (fortunately…, which is really saying something for a Renault owner!). Are you too stupid to see this? What I am saying is that the Renault will do what it is designed for. It will pull what it is designed for without someone having to say- "Oh, you've got so flick this switch at such or such a time, or the gears will break."! We have an expression in Europe, which applies equally to my own industry - "fit for purpose" which means that it is designed to do what it is supposed to do. The Germans are particularly strong on this (and my VW Beetle is the perfect example), so if we buy a vehicle to tow a particular weight, we do not expect it to break, or to have to mollycoddle it. We expect it to be "fit for purpose"!

"It's not unique to America. Get it!" Read my first post, you idiot. Does it not mention 'overdrive' in the UK? Have I ever said overdrive was unique to America, you idiot? Have I not also mentioned overdrive in other countries (etc.)? Your efforts have proven that you are totally ignorant of the auto industry outside of the US, and that you are incapable to make any meaning of it if you try via Google. So let's not beat about the bush; I will summarise in bullet-points, and let's hear what you think:

· 'Overdrive' has not been used in Europe in the last 15 years because it is a meaningless term.

· Bob c has already expressed very well the nonsense of the term 'overdrive' these days, but (no disrespect to Bob-c, an excellent fellow, for whom I have much respect) he is not all-the-way there. It is not just down to front-wheel-drive. The fact is: THERE IS NOTHING MAGICAL ABOUT A LESS THAN 1:1 GEARBOX RATIO. It means that the output speed of THE GEARBOX PART OF THE DRIVETRAIN has a ratio of less than 1:1, no more, and no less. It has no practical meaning. (…so why is it still used in the US?...Tell me why, if there is!!!).

· Usage in Europe between 1978 and 1998 was almost exclusively the preserve of Volvo, mostly for historical reasons (and rear-wheel-drive), the exceptions were very rare, and very short-lived due to unpopularity (see your research for proof).

· Usage in Europe from the 50s to the late 70s was mostly the preserve of the best performance cars (mostly British, like Aston Martin, Jaguar, Sunbeam & Triumph) and of Volvo, for obvious reasons, which I have already covered, but can explain again if you like.

· Usage in non-US and non-European countries (apart from India, where it does not exist for cars!!! occurs to some extent in countries that like to ape the US, but is rare in others.

· Usage outside the US these days is extremely rare (Give me proof and figures if you think otherwise).

· Does this not imply that "IT IS NOW AN AMERICAN THING!").

· All cars these days have overdrive transmissions. (So selling a car "with overdrive transmission" is like selling a care "with tires", or "with door handles"!)

· All US car dealers who sell cars without telling their customers that they have 'overdrive' transmissions are being dishonest, because all transmissions are 'overdrive'! (and apparently, 'overdrive' is much better, and therefore expected).

· All US car dealers who sell cars to their customers on the basis of the 'overdrive' transmission are being dishonest, because all transmissions are overdrive!

· Most Americans have very little understanding of 'overdrive', or how to use it. This is mostly due to what they have been "fed" by those in the industry (no offence, Autobroker), and things such as this: http://adland.tv/commercials/ford-automatic-overdrive-1980-030-usa

· As a salesman, I would really like to know how you manage to convince your customers that an auto-transmission with 'overdrive' (say 4-speed) is better than a 6, 7or 8 speed auto. Perhaps you could give me the spiel and tell me why it is better.

· So, going back to the OP's question, in your opinion, "Overdrive, is it an additional speed gear?" , if not, why?

By the way, I tried to hint at it before, but did you know that your Porsche991 user profile contravenes rule #1 of the CR4 Rules of Conduct? We are allowed only one profile, not several, otherwise we could, eg, vote ourselves for GAs and OTs. "Not Cricket", as we say here.

Ridiculous!

I'm sure that you could go to almost every country in the world and somewhere or other you will find a car with an O/D button (even if you just consider Volvo this is probably true), but this doesn't make them common, and it proves nothing. I once saw a tiger in the UK, but I don't think they are common here. I still maintain that 'overdrive, is vastly more prevalent in the US than anywhere else in the world (and non-existent in Europe), and you have not been able to prove otherwise.

And as for 13 years driving for the average Californian, yes, I have certainly driven more than 195,000 miles outside the UK, probably much more (I once covered 125,000 miles outside the UK in a five year period).

You knock Wikipedia, which is often written by people who know a thing or two, and is even successfully used by Oxford graduates and others who know how to use and interpret what they read on the internet, but in your feeble attempt to disprove me about 'overdrive' outside the US you post links to all sorts of forums (sometimes the most unreliable of places to find the truth in the first place) where we don't have a clue about the knowledge, understanding and reliability of the posters. Perhaps you should read Wikipedia?

I do not profess to be an expert in the field. I am just joining in with the discussion by expressing what I know and giving my opinion. Unlike some, I am quite happy to admit when I am wrong, and you may have noticed (or probably not!) that I have already corrected myself, or been corrected, several times in this thread. But you are supposedly an expert in this field, and it is your profession, so what is your excuse?

You also continually refuse to answer the very basic and crucial questions I have asked (obviously preferring to pick apart what I have written rather than concentrate on the issue we are discussing in this thread!). So, since you are such an expert in this field, why don't you finally tell us:

· Why do some people use the term 'overdrive', whilst others don't, for transmissions that are essentially identical, or do the same thing with the same number of gears and the same gear ratios?

· Why is the term used in the US but not in Europe

· You said: "In the US (since the 80's), the automakers use the term all the time"; so why do so many people not know what it is, what it does or how to use it?

· Are we addressing 'Autobroker' or 'Porsche991'?

The trucks are airport fire trucks. Between 1500 and 3,000 gallons of water. GVW ranges from 53,000 to 98,000 pounds. These are designated as HT750DRD. The trucks we retired last had input retarders installed. Driver training was fun.

"Now that you have it up to 70, pull the shift lever into first gear, and stand on the retarder pedal" The usual reply was "You first."

Not at all. The transmission would not drop to the next lowest gear untill the lower gear engine speed was at or below max governed engine speed. Just as if the driver had known exactly when to manually downshift. We had very good support from The local Allison dealer. He explained exactly how it should work, and the transmissions did. Something about trying to make them idiotproof. Same goes for putting it in reverse while still going forward. Shift inhibiters prevent this untill the engine is very close to idle speed, and vehicle speed is also almost 0. This I did not want to try, thank you. And this was with a non electric transmission. All done with hydraulics.

I amaware of five distinct types of braking retarders in automotive use.

1) The Jake Brake. A braking device that modifys the valve train of an engine to use the egnine's compression to slow down the vehicle. **

2) An input retarder used on Allison automatic transmissions. It redirects hydraulic fluid inside the transmission to cause increased turbulance in the torque converter to slow the vehicle down. **

3) An output retarder. Also used on Allison transmissions, but it consists of an additional chamber near the back of the transmission to slow the output shaft of the transmission instead of the torque converter.

4) An exhaust brake. Typicly a shut off valve in the exhaust pipe to raise the compression of the engine, therefore slowing it down. **

5) An electric retarder installed in the driveline between the rear axle, and the output of the transmission. It uses electrical current to stop the driveline from spimming.

** These retarders require downshifting the transmission to be most effective, as they work best at higher engine speeds.

One more overdrive tidbit. When gasoline engines(with much less torque) were more common in heavy trucks, there would be main transmissions, and auxilart transmissions. The common auxilary transmission I saw was a three speed gear box. It had under, over, and direct. Common practice was underdrive off road with a load. usually only needing the first two or three gears. City driving was done in direct. and the overdrive used once on a highway. Typicly only shifting the main transmission only in the two highest gears as hills required. The auxilary transmissions were not syncronized as I recall, making the syncronized transmission preferable for most shifting needs. Also the linkage on the auxilary was long, and not exactly like shifting a modern T5.

That story about the Tempest is left over from the movie "My Cousin Vinnie." 63 and earlier Tempests had a transmission mounted to the rear axle ala Corvair. Front engine, rear transaxle.

BTW, the engine in the early Tempest was half of the 389 V8. An inline 4. They wacked off one bank of cylinders. I do not remember if the engine stood straight up, or leaned over like the slant 6 from Chrysler.

Your friend is probably right about this. Quite a fascinating story. Not surprising they had a separate overdrive (I'd love to know what it was!) as the standard transmission was 3-speed manual with options for 2-speed auto or 4-speed manual. I did hear of 5-speed manuals being fitted.

Autobroker,

"……manual transmission, which typically doesn't use the term overdrive. This term is nearly always used for automatic transmissions…."

Nonsense! The term was nearly always used in North America for automatic transmissions simply because transmissions in North America were nearly always automatic. It just so happens that the term 'overdrive', when it was used in Europe, always applied to manual transmissions (for the same reason), so the manual/automatic element is irrelevant.

Furthermore, in your post #51, whilst teaching me all about overdrive, you seem to have repeated or paraphrased most of what I wrote in post #50 (except for the nonsense, I'll let you take credit for that).

If you google 'overdrive', no auto manufacturers feature in the first ten pages (maybe none at all? I don't know, I gave up after ten) and it is all about non-automotive overdrive.

Why have you changed your identity from Autobroker to Porsche991? Do you have any other identities? Surely there must be better ways to get yourself plenty of GA votes?

I was born just a few miles from your country, and have spent much of my life in Canada and the US. I'm sure I know more about your country than you know about Europe and beyond.

At last, you've got something right, and I admit my error. The Lexus in question has a '4-speed with overdrive' transmission (what we would call simply a 4-speed gearbox).

I've done plenty of googling, thanks. One thing I've noticed; If you google any auto manufacturer, plus overdrive, you will always get US sites, even for the likes of BMW, Audi, Honda, Lexus, etc. simply because they only use 'overdrive' for the American market, not for Europe (even though the gear ratios are pretty much the same).

I hope you got your kicks (simple for you?), but I can't believe you have wasted your time researching this. (Actually I can believe it!) Clearly it has taught you nothing! Since you appear to be reading what you want to see, not what I actually write in my posts, you may have missed the fact that I never actually said that overdrive never existed in Europe. On the contrary, I pointed out that that is where much of it started, and it was used a lot in the old days. Now, why don't you try using your google finger to see if you can find any evidence of overdrive being offered in the European market today, or even the last 10-15 years, rather than highlighting what might have occurred last century? Your question to "our European friends" exposes your ignorance and niaevity regarding all that is outside the US. It does you no justice, and perhaps you should take the example of your neighbours north of the border. Your googling, also, is not too convincing so far. Some comments on your links:

Opel Vectra: You have to be a little bit careful about what you take from a one-off forum posting like this. Is the car really an Opel, or a Vectra, where was it built, was it sourced via the USA, or elsewhere, is this guy really in Iraq? So many unknowns. But anyway, that car is almost 20 years old, and Opel/Vauxhall/GM haven't used the term overdrive in Europe this century, as far as I know. I get the impression you don't know much about googling outside the US! You really ought to be sure you have at least two or three references. One is meaningless. And what do you personally trust or believe from Iraq? But mostly, this confirms that they (non-US overdrives) are far but few, and a relic fro the past.

Volvo 700 and 900 : This is actually an interesting one. Volvo have a long history of overdrives. They were one of the first users of the (separate, bolt-on) Laycock overdrive unit, and probably used more over the years than any other car manufacturer. The 700 and 900 series (mentioned in the link) were the last of the rear-wheel drive models, produced from 1982-1998, and they still used the Laycock overdrive unit (on manual transmissions, at least). In Europe Volvo have not used the term 'overdrive' since 1998 (ergo, you are still highlighting old relics).

Ford Mondeo in UK (last I checked UK is in Europe)

(Aren't we clever! An American who knows where Europe is!), but another very rare, historical relic.

Yes, my main car is a 5-speed automatic. It is overdrive in the sense that the gear ratio of 5^th (and possibly also 4^th) is less than 1:1. But I don't think that Renault, or any of the French manufacturers for that matter, have ever offered overdrive, or used the term (in fact, I'm not sure that there is even a French word for overdrive). It does exactly the same as most of these 'automatic with overdrive' transmissions, but without the extra lights, solenoids, controllers and all the breakdowns that seem to come with these (judging by what our google searching has thrown up, it seems to be quite a big problem). I can hold it in 5^th in manual mode to prevent it hunting, or changing down too soon for my liking (although it will eventually change down to 4^th before any damage is done to engine/gearbox if I try to run it too slow or with too much load). I could hold it in 4^th in manual mode to prevent it shifting up to 5^th eg. when I'm pulling a heavy load uphill. But I don't normally have to do this. Usually it does what an automatic is supposed to do, and selects the right gear for the conditions (speed and load) without any lights or buttons.

Again, if you check to see what I have actually written, you will see that I have never claimed that Lexus is trying to "trick" people by using the word overdrive. I think that what I have said in previous posts is quite clear, and the culprits are the US auto manufacturers, and their minions (in sales and service?).

Yes, I am aware that "using the word overdrive here in the US is common". If you were not so stupid you would have noticed that that is exactly what I am saying.

Now, as someone in the industry, who supposedly knows a thing or two about this, please answer this question:

Why should I buy a car from you with an overdrive transmission? And what makes it better than the 5-speed auto transmission in my Renault (or, for that matter, the 4-speed overdrive transmission in my 1971 Beetle, which is unsurprisingly similar to its' forbears (or three bears, at least) from the 1930's/40's), and is this the same answer given vs. others who do not bleat about overdrive?

First of all, welcome to the insanity.

Did you read my post #56? Especially the last paragraph relating to parallel arangement of engine and transmission?

When one is looking to achieve fuel mileage by lowering the engine speed relative to road speed, the ultimate comparable specification is engine RPM per road speed.

Does it matter if we have a .5:1 transmission ratio in high gear if we then combine it with a 4:11 rear axle ratio? And then what if we change tires to increase the roll out distance by a third?

When auto manufactures place transmissions side by side with the engines, they no longer were constrained to a 1:1 radio for power transmission efficency, because they had designed another gear mechanism into the drivetrain.

So, it is now almost sensless to refer to a transmission as "overdrive" if it is not driven at the same speed as the engine. JMHO.

Hi Bob,

Not sure if you realize that Porsche991 is not a newbie, but actually 'Autobroker' himself (read the post!), posing as an outsider to boost his somethingorother (or GAs at least). What do you say about the people who have not spotted this?!!!