vrroooOOMMM vrm vrm vrrroooOMMM vrm vrooooOOOMMMMMMMM So the idea is you’ve just gotten a green light or are passing someone, you put the pedal to the metal and the automatic transmission changes gears, torques, jolts and sounds like a stick shift. This programmed option could be an adapted copy from a rally driver, drag racer or you, done on a mockup. The acceleration would not be optimal, but the effect might be impressive.-- FarmerJohn, Jun 28 2002 Manual & Automatic Gearboxes http://carcare.unip.../when/hycwgears.htmGeneric information [phoenix, Jun 28 2002, last modified Oct 21 2004] (?) Shiftless Drivers http://www.womanmot...ss-drivers-01.shtmlRegarding the popularity of automatic transmissions. [phoenix, Jun 28 2002, last modified Oct 21 2004] Non-performance car with automatic transmission http://www2.suite22.../~msocko/index.htmlIf you squint, you can almost see the little old lady driving. [bristolz, Oct 05 2004, last modified Oct 21 2004] Gallardo with e-gear automated transmission http://www.ultimate...ile=car.mv&num=1620Very close to what you seek, [FJ]. I wouldn't call it low performance or "pointless." [bristolz, Oct 05 2004, last modified Oct 17 2004] Audi RS6 http://autos.msn.co...delid=10680&src=vipNo manual transmission offered for this rocketship [bristolz, Oct 05 2004, last modified Oct 17 2004] How? Also, why?-- angel, Jun 28 2002 When the accelerator pedal is held firmly down, this option would override the usual transmission gear change schema. The gears would be changed at higher rpm and faster. Why? for the same reasons people choose other "sport" add-ons to their cars.-- FarmerJohn, Jun 28 2002 Apart from the jolting and sounding like a stick-shift, I though most automatics did this anyway.
Our 1980s (?) Morris Marina Estate used to change down if you floored the accelerator. I think they called it tap-down.
A newer car I had on hire (Vauxhall/GM/Opel 3 litre something) decided to change up while I was overtaking, leaving me stranded with no power on the wrong side of the road.
I guess the feature is not universal. I hate automatics.-- st3f, Jun 28 2002 Kick-down, whereby flooring the accelerator actuates a switch underneath the pedal which causes the trans to change down a gear, has been common on auto-trans for ever. Sport-mode automatics have been around for a lot of years, going back to the Porsche 'Sportomatic' system about 25 years ago. I'm not sure how you would get the trans to change gear 'faster' (I assume you mean 'more rapidly') as changes are virtually instantaneous anyway; it's only a small amount of lag in the fluid coupling to smooth out the jerk that delays the change.How would this be a 'sport' add-on?-- angel, Jun 28 2002 My brother has an Accord with "Honda-matic" transmission, which is apparently an automatic you have to shift anyway.-- waugsqueke, Jun 28 2002 Ahhh, kick-down, of course. Tap-down... Hee hee... <snort>.
I think FarmerJohn is after some difference in engine sound as well as performance but I think we will have to wait for his clarification to enlighten us. It's possible he's unaware of kick-down.-- st3f, Jun 28 2002 There's always Tiptronic transmissions which operate as both manual and automatic (but not at the same time and do require human intervention). Or you could put your automatic in 1st gear, 2nd, etc, but again there's that human touch thing.-- phoenix, Jun 28 2002 Stall converter.-- bristolz, Nov 08 2002 If I interperate this correctly, he is seeking an automatic that shifts harder under full throttle conditions than under normal cruise. This is a thoroughly baked idea as there are several gadgets on the market that allow you to alter the programming of todays electronic transmissions. A simple turn of the dial allows you to go from cruise mode to race mode, or something similar anyhow. This is even available on some cars from the factory, much like shocks that can be adjusted to firm the ride in sport mode. Personally, I agree with st3f, automatics are for little old ladies and have no business in any type of performance vehicle, therefore making them sound like a performance vehicle is pointless.-- WikdWaze, Oct 04 2003 Manual transmissions are good for keeping atop the powerbands of peaky engines but when the powerband is wide and the torque is plenty than I think an automatic is superior.-- bristolz, Oct 05 2003 bristolz, please show me a modern car with a "wide and plenty" powerband. It is a fact that manual transmissions get better economy due to significantly lower parasitic drag. They are also cheaper to maintain and repair. Manuals are also safer than automatics. I came very close to death on one occasion when the transmission in my vehicle decided to downshift at a most inopportune moment. Manuals are so much more fun to drive also. Ask anybody who opted for an automatic over a manual and they will tell you they bought it because it's easier to drive, not because the power of their car was so immense they didn't need a manual. I do, however, aknowledge that there are people physically incapable of operating a manual transmission, so the automatic does have it's place.-- WikdWaze, Oct 11 2003 Autos are vastly superior to manuals these days, especially as most drivers do not know how to drive a manual properly.
An auto beats a manual hands down from the lights every time (ignore prejudicial boy-mag timings)...especially every time as if you try and dump the clutch a few times trying to keep up with me your precious syncros will be scattered on the tarmac pretty sharpish!
Worried about upshifts? Use the lever, dummy! Just because you do not need to use it all the time does not mean you cannot use it all the time.-- timbeau, Jan 05 2004 people the only reason for automatic gearboxes is to allow the yanks on the road, seriously though manual gearboxes do provide better performance just look at any european car manufactures spec sheet for confirmation-- engineer1, Feb 16 2004 Auto is only good if you want to rip tree trunks out of the ground or something like that...
Manual all the way.... 6 speed.... mmmmmm-- KLRico, Feb 16 2004 [engineer1] As per my previous post, spec sheets are for a manual revved to peak and the clutch dumped - timing starting from the moment the foot is released from the clutch pedal. This will destroy a car very quickly if repeated.
The timings for an auto begins when the driver takes their foot off the BRAKE and then uses that same foot to press the accellerator. Of course, you can do this start on a fairly regular basis without too much damage but it also introduces an unfair delay.
The timings would be more honest if the driver used left foot braking and released the brake pedal when the engine was winding up against the brakes.
Lies, damn lines and 0-60 figures.-- timbeau, Feb 16 2004 Is this just designed for people too stupid to operate a clutch?-- NickTheGreat, Feb 17 2004 sequential gearbox would be cool and i have the impression that rally cars use these, back to defending the auto/manual as far as the 0-60 possibly they tend to be recorded using the slide your foot off the clutch realising it in a snapping motion rather than lifting the foot off.-- engineer1, Feb 17 2004 Note that in drag racing, if you're not using an automatic transmission, you're losing. Auto transmissions totally dominate the sport: humans can't shift fast enough. However, the faster the shift, the more "bang" you feel in your ass. Most street cars have a slower shift to give the engine more time to spin down during the shift.-- snarke, Mar 20 2004 Note that the most popular auto transmission in drag racing is the 2-speed PowerGlide. The later ones were bulletproof.
The 13-ton truck I drive has a 6-speed Allison automatic transmission behind a 275 HP Cat turbo diesel. It's not only more fuel-efficient than the manual-shift truck it replaced, but it accelerates much faster. I didn't think I'd like an auto trans in such a large vehicle (I drove the big ones for a few years, 9-speed and 15-speed manual transmissions behind 400 HP turbodiesels) but it's much less tiring.
If you want your automatic to sound and act like a manual, any competent transmission shop should be able to do the job, but they would also want to talk you out of it; such a change would reduce the life and reliability of the transmission.-- whlanteigne, Oct 02 2005 As I understand the auto transmission it seems that the torque converter is where the inefficiency really comes from. However, I believe most vehicles (my '91 does) have a TC lockup clutch that effectively bypasses the "slush" part of the "slushbox" during cruise. Besides, when you're accelerating the sloshing inefficiency is excusable since it allows your engine to work closer to its peak power RPM range, rather than dumping fuel into too little air.
I think the real problem with the auto is that it has fewer gear ratios in most cases. My auto has four, most manuals have five. So my automatic spans the gaps with heavy utilisation of the torque converter. My foot affects my economy greatly- by keeping my revs low (and the TC locked- I can tell when it isn't) I get around 18MPG. When I just set cruise control I get closer to 14MPG since it keeps revving into the slush.
So, [FarmerJohn], just find the wires that control the torque converter lockup and force it on. On my vehicle it's as simple as shorting two wires together. Without the damping action of the slush it'll act like dumping the clutch. I think it'd suck, and maybe even break things. No thanks.-- Souse Mouse, Dec 14 2005 //I get around 18MPG. When I just set cruise control I get closer to 14MPG// I'm giving automatics a bone for this reason alone.-- coprocephalous, Dec 14 2005 Nah, the manual doesn't get any better. I just have a fat pig of a vehicle with an inefficient engine.-- Souse Mouse, Dec 14 2005 if a "different sound" is what's desired, replace the standard muffler (silencer) with a glasspak, like a Thrush or a Cherry Bomb.-- whlanteigne, Jul 03 2006 my dad had a Saab with a "sprot button" which changed the shift points to redline whe you really wanted to punch it. lots of fun, but alas, baked.-- bleh, Jul 03 2006 www.rospa.com THE USE OF AUTOMATIC GEARBOXES Automatic gearboxes and modern derivatives are becoming more common but some drivers are uncertain as how to make the best use of them. These notes, outlining the expectations of the examiner, are designed to assist you get the most from your vehicle as you prepare for the advanced test. A reasonable understanding of the general principles of the automatic gearbox will enable you to make appropriate decisions based on the prevailing circumstances and the performance of your vehicle. The modern automatic boxes can contain anything from three to six different ratios and may also be enhanced with ‘Economy’ or Sport’ modes. They also have different names such as tiptronic, selectomatic, steptronic and multitronic. The change mechanism can be mounted on the floor or within the steering wheel/column. Manufacturers have invested heavily in these gear change systems and you should first refer to the owner’s manual for advice. Let us consider, briefly, the make-up of the automatic transmission. In the majority of cases this consists of a torque converter and a set of gears called planetary or epicyclical gear train. These are fitted to the car in place of a conventional clutch and gearbox. The torque converter, as the name implies, converts the torque or turning effort of the engine power through the gear ratios to the drive wheels. Basically, the torque converter consists mainly of an impeller, which is driven by the engine and a turbine that drives the gearbox. Each is bowl shaped and contains a number of partitions or vanes. They are mounted face-to-face in the oil filled gearbox but there is no physical contact between them. Put simply, when you press the accelerator you increase the speed of the impeller, which forces the gearbox oil through the vanes of the turbine, making it rotate. An increase or decrease in torque has the same effect as changing to a higher or lower gear This almost fluid connection between the engine, through the gearbox, to the drive wheels means that leaving the gear lever in ‘D’ when negotiating a hazard is not the same as leaving a manual gearbox in top gear. The majority of gear selector positions are marked: P PARK must never be engaged whilst the vehicle is in motion as it locks the transmission and prevents the car from moving. R REVERSE N NEUTRAL D AUTOMATIC DRIVE USING ALL FORWARD GEARS and a configuration of 1, 2, 3 and 4 for manual selection, or a symbol such as a plus or minus sign for upward or downward manual changes. For normal driving the lever can remain in ‘D’ and allow the transmission to make automatic adjustments according to road speed, engine loading and accelerator position.-- 3phase, Jul 31 2006 www.madabout-kitcars.com
A manual transmission (also known as a stick shift or standard transmission) is a type of transmission used in automotive applications. Manual transmissions often feature a driver-operated clutch and a movable gear selector, although some do not. Most automobile manual transmissions allow the driver to select any gear at any time, but some, such as those commonly mounted on motorcycles and some types of race cars, only allow the driver to select the next-highest or next-lowest gear ratio. This second type of transmission is sometimes called a sequential manual transmission.
Manual transmissions are characterized by gear ratios which are selectable by engaging pairs of gears inside the transmission. Conversely, automatic transmissions feature clutch packs to select gear ratio. Transmissions which employ clutch packs but allow the driver to manually select the current gear are called semi-automatic transmissions.
Contemporary automotive manual transmissions are generally available with between 4 and 6 forward gears and one reverse gear, although manual transmissions have been built with as few as 2 and as many as 7 gears. Some manuals are referred to by the number of forward gears they offer (e.g., 5-speed) as a way of distinguishing between automatic or other available manual transmissions. In contrast, a 5-speed automatic transmission is referred to as a 5-speed automatic.
Other types of transmission in mainstream automotive use are the automatic transmission, semi-automatic transmission, and the continuously variable transmission.
Manual transmissions come in two basic types: simple unsynchronized systems where gears are spinning freely and their relative speeds must be synchronized by the operator to avoid noisy and damaging "clashing" and "grinding" when trying to mesh the rotating teeth, and synchronized systems that eliminate this necessity while changing gears.
Unsynchronized transmission
The earliest automotive transmissions were entirely mechanical unsynchronized gearing systems. They could be shifted, with multiple gear ratios available to the operator, and even had reverse. But the gears were engaged by sliding mechanisms or simple clutches, which required skills of timing and careful throttle manipulation when shifting, so that the gears would be spinning at roughly the same speed when engaged; otherwise the teeth would refuse to mesh.
When upshifting, the speed of the gear driven by the engine had to drop to match the speed of the next gear; as this happened naturally when the clutch was depressed, it was just a matter of skill and experience to hear and feel when the gears managed to mesh. However, when downshifting, the gear driven by the engine had to be sped up to mesh with the output gear, requiring engagement of the clutch for the engine to speed up the gears. Double declutching, that is, shifting once to neutral to speed up the gears and again to the lower gear, is sometimes needed. In fact, such transmissions are often easier to shift from without using the clutch at all. The clutch, in these cases, is only used for starting from a standstill. This procedure is common in racing vehicles and most production motorcycles.
Even though automotive transmissions are now almost universally synchronised, heavy trucks and machinery as well as dedicated racing transmissions are still usually nonsynchromesh transmissions, known colloquially as "crashboxes", for several reasons. Being made of brass, synchronizers are prone to wear and breakage more than the actual gears, which are cast iron, and the rotation of all the sets of gears at once results in higher frictional losses. In addition, the process of shifting a synchromesh transmission is slower than that of shifting a nonsynchromesh transmission. For racing of production based transmissions, sometimes half the dogs on the synchros are removed to speed the shifting process, at the expense of much more wear.
Similarly, most modern motorcycles still utilise Unsynchronised transmissions. Synchronisers are generally not necessary or desirable in motorcycle transmissions. The low gear inertias and higher strengths mean that 'forcing' the gears to alter speed is not damaging, and the selector method on modern motorcycles (pedal operated) is not conducive to having the long shift time of a synchronised gearbox. Because of this, it is still necessary to synchronise gear speeds by 'blipping-the-throttle' when shifting into a lower gear on a motorcycle.
Synchronized transmission
A modern gearbox is of the constant mesh type, in which all gears are always in mesh but only one of these meshed pairs of gears is locked to the shaft on which it is mounted at any one time, the others being allowed to rotate freely; thus greatly reducing the skill required to shift gears.
Most modern cars are fitted with a synchronised gear box, although it is entirely possible to construct a constant mesh gearbox without synchromesh, as found in motorcycle for example. In a synchromesh gearbox, the teeth of the gears of all the transmission speeds are always in mesh and rotating, but the gears are not directly rotationally connected to the shafts on which they rotate. Instead, the gears can freely rotate or be locked to the shaft on which they are carried. The locking mechanism for any individual gear consists of a collar on the shaft which is able to slide sideways so that teeth or "dogs" on its inner surface bridge two circular rings with teeth on their outer circumference; one attached to the gear, one to the shaft. (One collar typically serves for two gears; sliding in one direction selects one transmission speed, in the other direction selects the other) When the rings are bridged by the collar, that particular gear is rotationally locked to the shaft and determines the output speed of the transmission. To correctly match the speed of the gear to that of the shaft as the gear is engaged, the collar initially applies a force to a cone-shaped brass clutch which is attached to the gear, which brings the speeds to match prior to the collar locking into place. The collar is prevented from bridging the locking rings when the speeds are mismatched by synchro rings (also called blocker rings or balk rings, the latter being spelled "baulk" in the UK). The gearshift lever manipulates the collars using a set of linkages, so arranged so that only one collar may be permitted to lock only one gear at any one time; when "shifting gears", the locking collar from one gear is disengaged and that of another engaged. In a modern gearbox, the action of all of these components is so smooth and fast it is hardly noticed.
The first synchronized transmission system was introduced by Cadillac in 1929. The modern cone system was developed by Porsche and introduced in the 1952 Porsche 356; cone synchronizers were called "Porsche-type" for many years after this. In the early 1950s only the second-third shift was synchromesh in most cars, requiring only a single synchro and a simple linkage; drivers' manuals in cars suggested that if the driver needed to shift from second to first, it was best to come to a complete stop then shift into first and start up again. With continuing sophistication of mechanical development, however, fully synchromesh transmissions with three speeds, then four speeds, five speeds, six speeds and so on became universal by the 1960s. Reverse gear, however, is not synchromesh, as there is only one reverse gear in the normal automotive transmission and changing gears in reverse is not required.
Internals
Like other transmissions, a manual transmission has both input and output shafts. Pairs of gears are attached to these shafts such that, when selected, will cause the output shaft to rotate at a given ratio of the input shaft speed. When a driver selects a gear, he is simply selecting a pair of these gears to be used; mechanical connections translate the driver's selection into an appropriate connection of gears and prevent more than one set of gears being engaged at any given time (as that would cause the transmission to lock). The teeth on gears of mass market automobiles are not straight-cut, but are helically cut, in order to reduce gear whine. Reverse gear often is straight-cut, however, leading to a characteristic whine from many cars when reversing.
In racing vehicles (most commonly those involved in drag racing), sometimes a trans-brake is incorporated, allowing the driver to lock the transmission into both first gear and reverse gear at the same time. This serves the purpose of allowing the driver to increase the engine speed without changing the vehicle's speed (much as one would do while in neutral, or while the clutch is disengaged), but being able to transfer as much of the resultant power to the tires in a shorter period of time.
The input shaft of a manual transmission comes from the clutch, and is connected to a layshaft. The lay shaft has one gear on its input end and several on the output end, usually one per selectable gear. The output gears of the layshaft connect to the drive gears. These are fixed in place on the output shaft, which leads to the differential and tires.
Manual transmissions are often equipped with 4, 5, or 6 forward gears. Nearly all have exactly one reverse gear. In three or four speed transmissions, in most cases, the topmost gear is "direct", i.e. a 1:1 ratio. For five speed or higher transmissions, the highest gear is usually an overdrive gear, with a ratio of less than 1:1. Older cars were generally equipped with 3-speed transmissions, or 4-speed transmissions for high performance models and 5-speeds for the most sophisticated of automobiles; in the 1970s, 5-speed transmissions began to appear in low priced mass market automobiles and even compact pickup trucks, pioneered by Toyota (who advertised the fact by giving each model the suffix SR5 as it acquired the fifth speed). Today, mass market automotive manual transmissions are essentially all 5-speeds, with 6-speed transmissions beginning to emerge in high performance vehicles in the early 1990s, and recently beginning to be offered on some high-efficiency and conventional passenger cars.
On earlier models with three or four forward speeds, the lack of an overdrive ratio for relaxed and fuel efficient highway cruising was often filled by incorporation of a separate overdrive unit in the rear housing of the transmission, separately actuated by a knob or button, often incorporated into the gearshift knob.
Clutch
In all vehicles utilizing a transmission (virtually all modern vehicles), a coupling device is utilized to be able to separate the engine and transmission when necessary. The clutch is what accomplishes this in manual transmissions. Without it, the engine and tires would at all times be inextricably linked, and anytime the vehicle is at a stop, so would be the engine. In a car the clutch is usually used by a pedal; on a motorcycle, a lever on the left handlebar serves the purpose.
* When the clutch pedal is fully depressed, the clutch is fully disengaged, and no torque is transferred from the engine to the transmission, and by extension to the drive wheels. This allows for the transmission's gears to be independent of the engine (spinning purely through momentum or, for any engaged gear, the motion of the vehicle). This allows for shifting without gear grinding. * When the clutch pedal is fully released, the clutch is fully engaged, and essentially all of the engine's torque is transferred. * In between these extremes, the clutch "slips" to varying degrees. Clutch slippage is useful, because the entire purpose the transmission serves is gear reduction. Because the engine and tires are designed to be linked in order to drive, one must dictate the speed of the other. If there was no slippage, the tires would dictate engine speed, and as such, getting a vehicle to move from rest would be extremely difficult. This slippage allows for the slow introduction of power, with less resistance introduced to the engine until enough momentum is built that the engine can operate normally without output reduction from the clutch. * Note: Automatic transmissions also utilize a coupling device, however, a clutch is not present. In these kinds of vehicles, the torque converter is used to separate the engine and transmission.
Gear selection
Floor-mounted shifter
In most modern cars, gears are selected through a lever attached to the floor of the automobile—this selector is often called a gearstick, gear lever, gear selector, or simply shifter. Moving this lever forward, backward, left, and right allows the driver to select any given gear. In this configuration, the gear lever must be pushed laterally before it is pushed longitudinally.
A common layout for a 5-speed transmission is shown below. N marks neutral, or the position where no gears are engaged. In reality, the entire horizontal line is a neutral position, although the shifter is usually equipped with springs so that it will return to the N position if not left in another gear. The R denotes reverse, which is technically a sixth gear on this transmission. There is usually a mechanism that only allows selection of reverse from the neutral position, so reverse will be less likely to be accidentally chosen when downshifting from 5th to 4th (or by someone used to a 6-speed transmission and trying to shift from 5th to the non-existent 6th).
Image:Manual Layout.PNG
This layout is called the shift pattern. The shift pattern for a specific transmission is usually printed on the shifter knob.
Another common five-speed shift pattern is:
Image:Manual Layout 2.PNG
Transmissions equipped with this shift pattern usually feature a lockout mechanism that requires the driver to depress a switch or the entire gear lever when entering reverse, so that he does not accidentally select it when trying to find first gear.
Most front-engined, rear-wheel drive cars have a transmission that sits between the driver and the front passenger seat. Floor-mounted shifters are often connected directly to the transmission. Front-wheel drive and rear-engined cars often require a mechanical linkage to connect the shifter to the transmission.
A 4-speed floor shifter is sometimes referred to as "Four on the Floor".
Column-mounted shifter
Some older cars feature a gear lever which is mounted on the steering column of the car. Many automatic transmissions still use this placement, but manual column shifters are no longer common.
Column shifters are mechanically similar to floor shifters, although shifting occurs in a vertical plane instead of a horizontal one. Column shifters also generally involve additional linkages to connect the shifter with the transmission.
Image:Manual Layout 3.PNG
The 3-speed shift pattern is typical of American cars, trucks, and vans produced with manual transmissions until the 1950s and 1960s. This pattern is not "intuitive", as the shifter has to be moved forward (into R) to make the car go backward (and vice-versa).
First gear in a 3-speed is often called "low," while third is usually called "high." There is, of course, no overdrive.
A 3-speed column shifter is sometimes referred to as "Three on a Tree".
Note that reverse in a car with a column shift is in nearly the same position as park (P) is on a car with a column-mounted gear selector with an automatic transmission.
Sequential manual
Some transmissions do not allow the driver to arbitrarily select any gear. Instead, the driver may only ever select the next-lowest or next-highest gear ratio. These transmissions often provide clutch control, but the clutch is only necessary when selecting first or reverse gear from neutral. Most gear changes can be performed without the clutch.
Sequential transmissions are generally controlled by a forward-backward lever, foot pedal, or set of paddles mounted behind the steering wheel. In some cases, these are connected mechanically to the transmission. In many modern examples, these controls are attached to sensors which instruct a transmission computer to perform a shift—many of these systems can be switched into an automatic mode, where the computer controls the timing of shifts, much like an automatic transmission.
Motorcycles typically employ sequential transmissions, although the shift pattern is modified slightly for safety reasons. In a motorcycle the gears are usually shifted with the left foot pedal, the layout being this:
5 4┘ 3┘ 2┘ N 1
The pedal goes one step - both up and down - from the center, before it reaches its limit and has to be allowed to move back to the center position. Thus, changing multiple gears into one direction is accomplished by repeatedly pumping the pedal, either up, or down. Although neutral is listed as being between first and second gears for this type of transmission, it "feels" more like first and second gear are just "further away" from each other than any other two sequential gears. For inexperienced riders, this can lead to difficulty in finding neutral. The reason neutral does not actually have its own spot in the sequence is to make it quicker to shift from first to second when moving. You will not accidentally shift into neutral. The reason for having neutral between the first and second gears instead of at the bottom is that when stopped, the rider can just click down repeatedly and know that they will end up in first and not neutral.
Semi-manual
Some very new transmissions (BMW's Sequential Manual Gearbox (SMG) and Audi's Direct-Shift Gearbox (DSG), for example) are conventional manual transmissions with a computerized control mechanism. These transmissions feature independently selectable gears but do not have a clutch pedal. Instead, the transmission computer controls a servo which disengages the clutch when necessary.
These transmissions vary from sequential transmissions in that they still allow nonsequential shifts: BMWs SMG system, for example, can shift from 6th gear directly to 4th gear when decelerating from high speeds.
Comparison with automatic transmissions
Manual transmissions are typically compared to automatic transmissions, as the two represent the majority of options available to the typical consumer. These comparisons are general guidelines and may not apply in certain circumstances. Additionally, the recent popularity of semi-manual and semi-automatic transmissions renders many of these points obsolete. It should be kept in mind that many some of these points are true of "conventional" automatic transmissions which shift gears and are coupled to the engine with a torque converter but are not a true comparison or do not apply to other kinds of automatic transmissions, like the continuously-variable transmission.
Advantages
* Manual transmissions are typically more efficient than automatic transmissions. This is because manuals generally involve a clutch instead of a torque converter, which can cause significant power losses and because an automatic transmission introduces parasitic losses through the high pressure hydraulic pumps it requires. This results in both better acceleration and fuel economy. * It is generally easier to build a very strong manual transmission than a very strong automatic transmission. Manual transmissions usually have only one clutch, whereas automatics have many clutch packs. * Manual transmissions are generally significantly lighter than torque-converter automatics. * Manual transmissions are typically cheaper to build than automatic transmissions. * Manual transmissions generally require less maintenance than automatic transmissions. * Manual transmissions normally do not require active cooling, because not much power is dissipated as heat through the transmission. o The heat issue can be important in certain situations, like climbing long hills in hot weather, particularly if pulling a load. Unless the automatic's torque converter is locked up (which typically only happens in an overdrive gear that would not be engaged when going up a hill) the transmission can overheat. A manual transmission's clutch only generates heat when it slips, which does not happen unless the driver is riding the clutch pedal. * A driver has more direct control over the state of the transmission with a manual than an automatic. This control is important to an experienced, knowledgeable driver who knows the correct procedure for executing a driving manoeuver, and wants the machine to obey his or her instructions exactly and instantly. o An example: the driver, anticipating a turn, can downshift to the appropriate gear while the steering is still straight, and stay in gear through the turn. This is the correct, safe way to execute a turn. o Another example: when starting, the driver can control how much torque goes to the tires, which is useful for starting on slippery surfaces such as ice, snow or mud. This can be done with clutch finesse, or possibly by starting in second gear instead of first. The driver of an automatic can only put the car into drive, and play with the throttle. The torque converter can easily dump too much torque into the wheels, because when it slips, it acts as an extra low gear, passing through the engine power, reducing the rotations while multiplying torque. o Yet another example: passing. When the driver is attempting to pass a slower moving vehicle by making use of a lane with opposite traffic, he can select a lower gear for more power at exactly the right moment when conditions are right to begin the manoeuver. Automatics have a delayed reaction time, because the driver can only indicate his intent by pressing the throttle. The skilled manual transmission driver has an advantage of superior finesse and confidence in such situations. * Many people prefer driving a car with a manual transmission because it provides a more direct interaction in the driving experience * Many people feel that driving a manual forces the driver to pay more attention to the road and to other cars, making it more difficult to become distracted. o A related point is that the driver of a manual transmission car can develop an accurate intuition for how fast the car is traveling, from the sound of the motor and the gear selection. It's easier to observe the lower speed limits like 30 km/h and 50 km/h without glancing at the instrumentation. * Cars with manual transmissions can be started when the battery is dead by pushing the car into motion (or allowing it to roll down a hill) and then engaging the clutch in third or second gear. o Caveat 1: if the battery is too drained, there is the risk that the spark plugs won't fire during the first few strokes of the engine, and consequently that unburned fuel-air mixture will escape into the exhaust system, where it can later ignite, possibly damaging or destroying the catalytic converter. Consequently, push-starting should be regarded as an extreme emergency measure. However, the choice is there, and so this can be regarded as an advantage of a manual transmission automobile in spite of the inherent risks. o Caveat 2: it can't be assumed that every car with a manual transmission can be started this way. Some modern cards have engine-management electronics which must be active in order for the engine to start. These components might not obtain sufficient power from the push. * Manual transmissions work regardless of the orientation angle of the car with respect to gravity. Automatic transmissions have a fluid reservoir (pan) at the bottom; if the car is tilted too much, the fluid pump can be starved, causing a failure in the hydraulics. This could matter in some extreme off roading circumstances.
Disadvantages
* Manual transmissions require more driver interaction than automatic transmissions. * A driver may inadvertently shift into the wrong gear with a manual transmission, potentially causing damage to the engine and transmission as well as compromising safety. * Manual transmissions are more difficult to learn to drive as one needs to develop a feel for properly engaging the clutch. * The smooth and quick shifts of an automatic transmission are not guaranteed when operating a manual transmission. * Manual transmissions are slightly harder to start when stopped upward on a hill, but this is easily overcome with a little experience.
Applications and popularity
Many types of automobiles are equipped with manual transmissions. Small economy cars predominantly feature manual transmissions because they are relatively cheap and efficient, although many are optionally equipped with automatics. Economy cars are also often powered by very small engines, and automatic transmissions can make them comparatively very slow.
Sports cars are also often equipped with manual transmissions because they offer more direct driver involvement and better performance. Off-road vehicles and trucks often feature manual transmissions because they allow direct gear selection and are often more rugged than their automatic counterparts.
Very heavy trucks also feature manual transmissions because they are efficient and, more importantly, can withstand the severe stress encountered in hauling heavy loads.
Conversely, manual transmissions are no longer popular in many classes of cars sold in North America, although they remain dominant in Europe. Nearly all cars are available with an automatic transmission option, and family cars and large trucks sold in the US are predominantly fitted with automatics. In Europe and Asia most cars are sold with manual transmissions. Most luxury cars are only available with an automatic transmission. In situations where automatics and manual transmissions are sold side-by-side, the manual transmission is the base equipment, and the automatic is optional—although the automatic is sometimes available at no extra cost. Some cars, such as rental cars and taxis, are nearly universally equipped with automatic transmissions in the US.
Driving technique
See Manual transmission driving technique.
Maintenance
Because clutches use changes in friction to modulate the transfer of torque between engine and transmission, they are subject to wear in everyday use. A very good clutch, when used by an expert driver, can last hundreds of thousands of kilometres. Weak clutches, downshifting, inexperienced drivers, and aggressive driving can lead to more frequent repair or replacement.
Manual transmissions are lubricated with gear oil, which must be changed periodically in some cars, although not as frequently as the automatic transmission fluid in a vehicle so equipped. (Some manufacturers specify that changing the gear oil is never necessary except after transmission work or to rectify a leak.)
Gear oil has a characteristic aroma, due to the addition of molybdenum disulfide compounds, to lubricate the large degree of sliding friction seen by the teeth due to their helical cut, which in turn is done to eliminate the characteristic whine of straight cut gears. Some manufacturers, however, such as Honda, do not use this additive in their gear lube, specifying regular motor oil until recently, and now their own brand of gear lube which seems to be an enhanced version of motor oil. On motorcyles with "wet" clutches (clutch is bathed in engine oil), there is usually nothing separating the lower part of the engine from the transmission, so the same oil lubricates both the engine and transmission.
********** The two previous articles serve to make my point that automatic transmissions (AT) can be faster and more efficient than manual transmission (MT). Synchromesh allows AT users to shift without worrying about mashing or grinding gears...remember it is an AT. This 'automatic' technology is used in current MTs. ATs have fuzzy logic computers along with dozens of transmission-fuel maps, that is, the AT shifts at predetermined (AT-fuel map technology) shift points or learned shift points (fuzzy logic technology).
For those don't want to read the long articles I will briefly summarize what I have observed and determined:
Note: I have a 2005 Nissan Xterra 2-Wheel Drive, 265hp / 285 ft-lb., 5-Speed AT
Leaving an AT gearbox in "D" amounts to telling the AT to use all 5 forward gears. 5th gear is called "overdrive" but it really is simply top gear. In short, 5 gears means that the engines power and torque are distributed over 5 gears.
I don't want to use top gear in town. So, I shift to 4th gear and leave it there. Now, my power and torque are spread out over 4 gears. Each gear now has to handle more torque/power and to accomodate this the shift points have now been raised to upshift at higer RPMs. In short, I have a stronger acceleration launch from a standing stop at street intersection stops, because I'm limiting myself to only 4 gears. Lower gears means more torque which translates to harder acceleration force.
If I leave it shifted in 3rd I can really kick ass. I can smash little cars, cruiser motorcyles, bigger trucks pretty much people that don't know how to drive. In a manual do you really need to get above 3rd gear in city driving. My driver's manual says I can drive up to 62 mph 3rd gear [2nd gear => up to 71 mph (yeah I know this value is counter-intuitive but it's right), 1st gear => up to 45 mph]. In this gear the engine torque is so strong that the whole chassis rolls from the engines reaction torque on the body, i.e. torque steer. I can launch so hard and the shifting points are now at higher RPMs. In fact, the fuzzy logic learns my driving habits because I hold RPMs until they hit 4,000 RPM to attain maximum torque and now the AT shift right at the point just the way I like it.
I don't ever use 2 or 1 because I never need that torque range and the RPMs would be unreasonable for normal driving use.
**** Finally, an end all argument to this debate of which is better: AT or MT?
Formula 1 cars utilize semi-automatic gearboxes which are linked to 3.0L - 1000 hp engines. That's right, 3.0L = 1000 hp! Massive. They use the same technology in commercial ATs. They shift faster than humanely possible (50 milliseconds) and if it weren't for the transmission's ability to synchromesh and downshift automatically, F1 driver's could over rev the engine or be in wrong gear.
MT gearboxes are ancient technology. Let's forget about technology created in the early half of the 1900's and use the good stuff. Formula 1 employs the world's most talented engineers...most with PhD's, I imagine. For those unfamiliar with Formula 1, it is the worlds largest sport with Mercedes, Honda, Toyota, BMW, Renault, to name a few, as manufacturers and team owners. F1 is on the cutting edge of automotive technology.
These engineers know what's up. All nay-sayers of AT technology ask yourselves this question "Why don't F1 designers use MT?" Well, it's how I've been arguing: MT are slow and inefficient technology.
Semi-automatic means it can be shifted manually by using clutch paddles behind the steering wheel. Many commercial vechicles allow this to be done and are essentially sequential shifting ATs. Just like in all modern racing cars.
Sincerely, I Love Machines-- 3phase, Jul 31 2006 good point [3phase].-- methinksnot, Jul 31 2006 random, halfbakery