Manual Vs. Automatic Transmissions: Which Should I Drive?

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Almost everyone has heard the terms “automatic” and “manual transmissions” when discussing automobiles, and it not news that the majority of cars on the road today utilize automatic transmissions, even though they are quite a bit newer than their relative manuals. The automatic transmission is often a technology we take for granted because it allows us to forget about the vehicle and concentrate on the road, traffic, and even the radio. What is also often forgotten is its origins. This technology did not just spring up overnight. It was the work of many engineers and technicians that developed the first transmission and continued to make numerous innovations to produce today’s transmission.

Submitted: May 16, 2010

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Submitted: May 16, 2010

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Automatic or Manual – Which Should I Drive?

By Gregg Roemhildt; Published: May 16, 2010

Introduction:
Almost everyone has heard the terms “automatic” and “manual transmissions” when discussing automobiles, and it not news that the majority of cars on the road today utilize automatic transmissions, even though they are quite a bit newer than their relative manuals. The automatic transmission is often a technology we take for granted because it allows us to forget about the vehicle and concentrate on the road, traffic, and even the radio. What is also often forgotten is its origins. This technology did not just spring up overnight. It was the work of many engineers and technicians that developed the first transmission and continued to make numerous innovations to produce today’s transmission. To understand the first transmissions, we must first look at the basics behind a working transmission.
The Basics:
It all begins with the engine.The engine produces the force to the transmission and the tires. Controlling the engine speed or revolutions per minute (RPM’s) is just a matter of giving the engine more or less fuel with the gas pedal. Connected directly to the engine with a spinning shaft is the transmission. Connected to the transmission is the rear or front wheels, depending on the vehicle. There are multiple sets of complicated gear-sets and shafts inside the transmission. But let’s first imagine that none of this is there. Instead it is just one shaft connecting the engine to the rear wheels. This would be like driving in first gear everywhere; the RPMs would be high and the vehicle would be very inefficient. Instead we have that central piece between the engine and the wheels that is called the transmission because it “transmits” the torque (force of the spinning driveshaft) and speed from the engine into a different torque and speed applied to the driveshaft.
The entire purpose of the transmission is to change the ratio of speed and torque between the input shaft (from the engine) and the output shaft (to the wheels). This simply means that while the engine may be spinning at 3000 RPMs, the output shaft may be spinning at a much slower rate, depending on the current gear ratio in the transmission. Modern day vehicles generally have a ratio of 12:1 in first gear (the output is spinning twelve times slower than the engine.)In order to accomplish this, different sets of gears are used to adjust speed. Imagine there is a small gear spinning in space. The teeth of this smaller gear line up with a much larger gear. Although this small gear may be spinning at a fairly fast rate, the larger gear’s speed is obviously going to be much slower. This is the basic idea behind the transmission of power, which utilizes multiple sets of these varying sizes or gears.
One more essential part to the transmission is the clutch. This is the middle man between the engine and the driveshaft and is generally controlled by a lever or a pedal in a manual transmission. An automatic generally contains several clutches which are controlled automatically. To picture a clutch, think of two metal discs, each connected to a shaft (see Figure 1). One disc is always spinning because it is connected to the engine (disc on the left) while the other one can slide up against this first to engage the vehicle in motion and can be pulled away to disengage (disc on the right). The design of the clutch is based on friction between these two discs.
Understanding the basic mechanics of a transmission will be helpful as we look at the history of these machines starting with the first manual transmissions. Following closely behind manual transmissions were the first forms of automatic transmissions.Then we will look at present day technologies involved in these machines and how they work. After we have an understanding of the basics behind the gears, we will learn the differences in driving an automatic versus a manual and the advantages of each in certain situations. There are a few key differences in between these machines worth noting. Although some may claim manual transmissions are more difficult to drive, they do in fact have many advantages that place them in an arguably higher rank than automatics.
Transmission History:
One fact I found interesting when researching transmissions was that they were actually invented for the gasoline engine. Before this invention, there were the steam engine and the electric motor, neither of which had anything like a manual or automatic transmission because in both of these vehicles, the driving forces were connected directly to the wheels. The steam engine “can start a long line of large railroad cars into motion without the necessity of going through a gear train” or a transmission. “The electric motor…develops its greatest turning effort when it is forced to rotate the slowest.” In contrast, “the gasoline engine is incapable of developing much power at low speeds” (Chicago 5). Instead, most of the torque is produced in higher RPMs. This creates a need for transmissions because starting out, a gas engine has little power and the speed of the output shaft must be greatly reduced. Once the engine has accelerated, torque increases and a small gear ratio becomes unnecessary so the vehicle is shifted into higher gear. This repeats until the vehicle reaches a comfortable and efficient driving speed with low RPMs.
Although the first transmissions were crude, they were definitely a step up from the earlier solution, which was a number of belts/chains and pulleys placed beneath the vehicle. As you could imagine, this type of mechanics underneath the car created many problems. As mentioned previously, the manual came first as it is the simpler of the two. The invention of “the modern transmission was introduced by a pair of Frenchmen—Louis-Rene Panhard and Emile Levassor—in 1894” (Schultz 38). A few years later, Louis Renault improved the design by replacing the chain drive to the rear axle with a metal shaft and adding a differential to the rear axle. The differential, which is currently used in modern vehicles, allows the rear wheels to spin at different speeds for turning.
Compared to today’s vehicles, shifting these vehicles was much more complicated. Because of this, they were also difficult to drive. The engines back then did not have an electrical start; instead these had to be cranked by hand. Also, there was no such thing as a smooth ride, especially when shifting gears. When the clutch was released, the result was often a violent jolt when the gears meshed that was quite straining on not only the transmission and the vehicle, but also its passengers. These earliest manuals demanded nearly constant maintenance because of sheared gears, worn out clutches, and regular stalling. A common phrase heard on the streets in these days was “Get a horse!” (Chicago 5). Automobile makers realized that if they wanted to sell gasoline powered vehicles, then they would need to develop an easier way to drive them.
This brings us up to the invention of the early automatics. One of the first solutions developed was the model known as the “friction wheel design.” Instead of using gears to transfer the power, it basically had two cement-like discs placed perpendicular to each other. No shifting was necessary and speed was controlled by sliding one of the discs either towards or away from the center of the other. What this would do is increase the radius of the driving disc which would increase the speed at which the wheels spin. This model allowed for an infinite number of speeds never had to deal with the sudden jerks from gears locking. The friction wheels also enabled the vehicle to come to a complete stop without any real problem. But one major flaw to the friction wheel design was the rate at which the discs lost their friction; this created an increase in maintenance because it would require the user to buff up the discs repeatedly and increase friction.
Another early design, which was quite a bit more complicated, was the Owens magnetic transmission. “It was produced by the Baker automobile company from 1915 to 1921” (Albers). This engine basically worked similarly to an electric motor, except the electricity was produced from the engine instead of being supplied by a battery:
[An] electrical generator connected to a horseshoe-shaped magnet, the ends of which stick straight forward. Situated between the prongs of the magnet is a steel armature connecting to an electrically powered motor…Power coming from the engine produces electricity and causes the magnet to spin. The electrically charged spinning magnet imparts this energy to the electric motor's armature, causing it to spin via magnetic imbalance (Albers).
The most interesting and beneficial feature of this system was that there were no locking parts; shifting gears was incredibly smooth and barely noticeable. Maintenance, on the other hand was comparable to the earlier models because the magnetic and electric parts were fairly expensive for the time.
As awkward and unsophisticated as these early transmissions may seem, they were advanced for the time period. Compared to the transmissions found in today’s vehicles, they still had miles to go. These first steps were all necessary because each of these new developments was an important step to the modern systems we use on a daily basis.
Modern Transmissions:
Modern transmissions use features that early developers never could have dreamed. Instead of a mechanical control system, modern technology utilizing computers and complex mechanics is applied. This technology has made it both easier and much more comfortable to drive a vehicle than in earlier times, and the ease of use has made the automatic transmission the most popular vehicle on the market. That being said, manual transmissions are still popular for a few reasons as well.
The idea behind modern manual transmissions has not changed much from its original design.Despite a few minor differences, the concepts discussed in previous sections remain the same. Let’s first recall the most important part of the manual transmission: the clutch. The clutch is the middle point between the engine and the driveshaft, which can be engaged and disengaged by sliding the two metal discs against and away from each other. Therein lies the main problem with the clutches. While the clutch is engaged, and the vehicle is in or out of gear, the two plates are completely snug with each other. However, while they are being slid together or pulled apart, there is some slippage between the two and wear occurs. The earliest designed clutches wore out very quickly because the materials used were similar to a friction wheel design mentioned before. Later designs use much stronger materials: “From the 1950 and the 1960s, you could count on getting between 50,000 and 70,000 miles from your car’s clutch. Clutches can now last for more than 80,000 miles if you use them gently and maintain them well” (Nice & Bryant). In addition to the modification in clutches, many changes have been made to the transmission itself, mostly involving minor changes in gear ratios to increase maximum power output, smoothness, and efficiency. Also the number of different speeds in a transmission has increased with most of today’s transmissions varying from four to six. In some newer models, “there are now even seven- and eight-speed transmissions being introduced by Mercedes-Benz and Lexus” (Laspina 1).
The real changes seen in transmission development were focused on automatic transmissions. As mentioned previously, while manual transmissions have a clutch that completely disconnects the engine from the wheels, automatics are continuously engaged. While early designs used the friction wheel and other creative solutions such as the Owens magnetic transmission, modern vehicle’s use a device known as a torque converter:
A torque converter is a type of fluid coupling, which allows the engine to spin somewhat independently of the transmission. If the engine is turning slowly, such as when the car is idling at a stoplight, the amount of torque passed through the torque converter is very small, so keeping the car still requires only a light pressure on the brake pedal (Nice).
In simpler terms, imagine a windmill that is propelled by air flow. If the wind speeds up, more force is applied to the blades of the windmill and it spins faster. The same goes for a torque converter, which looks similar to a fan on the inside. The engine drives a fluid pump that forces oil into the disc-shaped torque convertor and drives the fan shaped pieces inside. While the engine is at a low speed, there is little force on the fan and it is easy for the brakes to stop or hold the vehicle in place, and the operator never has to worry about grinding gears or damaging a clutch.
The second and more complicated section of the modern automatic is the area that controls the speed of the vehicle by changing gear ratios. Automatic vehicles still have the need (and capability) to change gears to control the speed for the same reasons as the manual, except they require no driver interaction (besides forward, reverse, and park). Gear ratios in automatics are changed by a complex interaction of gear sets, clutches, and shafts. Automatics utilize a special set of gears known as planetary gear sets. Without going into any major details, these are quite difficult to visualize. One planetary set (See Figure 2), which generally contains between around five separate gears, can output several different gear ratios by varying input and output gears. In order to change input and outputs, multiple mechanical hydraulic powered clutches are used to engage and disengage certain parts of the planetary set.
Operation and Control:
Now that we know how transmissions work, let’s put that information into action and find out how to drive one, and what’s going on behind the levers and pedals. To begin, we will look at the automatic. In an automatic vehicle, there are basically three controls that manipulate the speed of the vehicle. There is the shift lever, the brake pedal, and the accelerator. When the shift lever is moved from Park, the driveshaft is unlocked and the vehicle becomes free to move. Almost always, the brake pedal is required to shift from Park for this reason. Shifting into Neutral disconnects the driving gears from the engine and allows the vehicle to roll without any influence from the engine.
Other choices with the shift lever include the Reverse and Drive gears, and most automatics also have at least two specific gear choices: 1 and 2. Placing the shift lever in Reverse activates the set of planetary gears that reverse the engine’s motion and powers the drive shaft opposite that of the forward motion. Placing the vehicle in Drive activates the automatic gear control that will automatically control the gear depending on a combination of how fast the vehicle is going and how far the accelerator is pressed. Placing the shift lever in gears one or two will lock the transmission in one of these gears. This is useful for coasting down steep hills because the engine will slow the vehicle while locked in a lower gear and this will help to save the brakes.
For some, driving a manual will come naturally and the concept is simple. For everyone else, however, this skill will take some time and practice. The key to learning to drive a manual is understanding the logic behind the pedals. As mentioned before, the biggest problem and cause for repairs in a manual is clutch slippage. Therefore, trying to avoid this by using the clutch appropriately and not developing any bad habits will save a lot of time and repair money. How do we use the clutch appropriately? Recalling from earlier, we use the clutch pedal when we are changing gears. It works like this: to start, we use the clutch and the stick to place the vehicle in first gear. Then, just like in an automatic we use the accelerator to speed up the engine. Unlike the automatic, however, we must change the gears manually once a high rpm is reached. The clutch should be pressed, the accelerator released, and the gear shifted up. Once the vehicle has been placed in second gear, then and only then we release the clutch and once again apply the accelerator. This process repeats until an appropriate gear is reached: clutch, change gears, release clutch, and accelerate (repeat).
When coming to a stop, or just slowing down, the opposite order is used. Imagine the vehicle is in fifth gear and coming to a stop from a highway. The brake must be used to slow the vehicle down; however, eventually the vehicle’s engine will not be able to produce the power to stay in fifth gear. In this situation, downshifting must be used, which is another important skill in driving a manual. Opposite of accelerating, the shift will occur when the engine speed is slow and the brake should be pressed at a constant pressure the entire time. From fifth gear, the operation should be somewhat like this: apply clutch, downshift to fourth, release clutch, brake, apply clutch, downshift to third, brake, etc. Once the vehicle is about to come to a stop, and the driver has successfully downshifted to first, or second (sometimes it is not necessary to downshift completely), the clutch must be pressed to disengage the engine or it will stall. For long periods of stopping (such as a red light), it is generally a good idea to move the shifter into neutral and release the clutch. Just be ready to shift back into gear when the light turns.
There are a few things to keep in mind when driving a manual. Number one is do not “ride the clutch” while driving. This term refers to a bad habit often developed by new drivers. This includes pressing the clutch in slightly or not quite releasing it when changing gears and driving with a foot slightly pressed on the clutch. By keeping the clutch slightly pressed, the clutch will actually start slipping slightly which will cause some unneeded clutch wear. Another thing to keep in mind is driving or parking on an incline. In some situations, it will be necessary to come to a stop on an incline. As you may have guessed, this is also different in a manual. Because once the vehicle has stopped, and the clutch is applied, or the vehicle is in neutral, there is nothing propelling the vehicle forward like in an automatic and the vehicle will roll. It is a good idea in this situation to press the brake. A similar situation is parking a manual vehicle on an incline. First, manuals do not have a parking brake built into the transmission itself. Instead they only have the lever based parking brake. On an incline, this should always be used to prevent the vehicle from rolling. Another useful brake is the transmission itself. “[A] manual car should always (always!) be left in first or reverse when parked…” (Lydia). In general this rule can be used along with the parking brake if on an incline.
Finally, in order to change gears, there is a general pattern all manuals share. The lever known as the stick will have what is referred to as the “H” pattern. This name comes from the shifting pattern of earlier models of our modern manual transmissions. These early vehicles only had four gears (3 forward and reverse) and were (and still are) changed by moving the lever to any of the four points of the H. Generally, modern transmissions have a total of six gears (five forward and reverse). the pattern is more of an extended H and looks something like the picture on the right. First gear is usually to the right and forward or up according to the diagram, with second to the right and back (or down), with third in the middle and forward, etc. and with reverse to the left and back. Different models and companies sometimes vary this pattern so usually there is a helpful picture of the shift order on the top of the lever itself.

Pros and Cons: Automatic Vs. Manual:

When looking at the number of vehicles on the road, it is obvious automatics have the majority in both vehicles sold and driven today. To understand this reasoning, let’s look directly at the pros and cons of each. The biggest advantage to the automatic transmission is the user-friendly control. What could be simpler than two pedals and a steering wheel? In certain situations, such as stop and go traffic, the automatic definitely has the advantage because the vehicle can remain in gear while stopped and can also be accelerated without changing any gears.
On the other hand, manuals also have quite a few advantages. “A manual transmission can deliver better fuel economy and acceleration. But there can be big differences in how the shifter and clutch feel and operate, so [the driver should] try before [he or she buys]” (Fuel Economy). Depending on how the vehicle feels for the driver, the vehicle may get better (or worse) mileage. Unlike the automatic, the driver is in direct control of the speed and gear and with practice can make more intelligent decisions than an automatic ever could. One such example would be driving up a sharp hill. With an automatic, pressing the gas pedal down far enough causes the transmission to shift down a gear. Once the pedal is released due to the vehicle reaching an appropriate speed, the transmission will shift again, this time back up a gear. In a manual, the driver would make an intelligent decision to stay in the lower gear throughout the incline. Quite often in similar situations, automatics tend to shift needlessly, which brings us up to another advantage of manuals. Driving the automatic shifting mechanisms requires extra power whereas in the manual shifting is powered by the driver. This is one of the reasons manuals tend to be more fuel efficient and get better mileage. On a different note, one other advantage is lower purchase, repair, and maintenance costs. Manuals have significantly less moving parts and are much easier to repair when damaged.
Of course, with these benefits, there are also negatives. When looking at the automatics, one such negative is a higher cost. All those moving parts inside the a.t. will increase the cost for both initial purchase and any transmission repairs. However, when selling a used automatic, generally the seller can make a little more money than if the vehicle were a manual for two reasons. The first is the same as before: a higher initial cost raises the price for resale. The other is today’s higher demand for an automatic will slightly raise the resale price.
On the other hand, manuals also have their disadvantages. According to ConsumerReports.org, “Manual transmissions are available on only a relatively few models, which narrows your choices. They are typically found on small cars and sports cars” (Fuel Economy). Manuals also can be problematic when driving through heavy traffic due to the constant clutch operation. Pumping the clutch and changing gears repeatedly can become quite difficult for the inexperienced driver. The presumption that manuals require special skills is often the biggest reason people choose manuals over automatics. However, newer models have begun to become easier to use with new features such as “the Mini and Subaru, [which] come with a helpful hill-holder feature” (Fuel Economy).
Conclusion:
Quite often it seems people in search of a vehicle automatically will choose an automatic transmission because they feel it is too difficult to learn to drive a manual. It is true that both forms have their pros and cons and each should be considered before making a decision. At a glance, automatics may seem like the best option because of their ease of use compared to the manual. However, learning to drive a manual can be much more enjoyable and exciting when taking long trips. Other benefits, including cheaper purchase and repair costs and better fuel mileage, also help to balance the weight of learning how to drive. Once the obstacle of mastering the manual has been overcome, the manual transmission truly seems like the better option.
Citations:
Albers, John. "How Does an Owen Magnetic Car Work? | EHow.com." EHow | How To Do Just About Everything! | How To Videos & Articles. EHow.com. Web. 08 Mar. 2010.
Brain, Marshall. "HowStuffWorks "How Manual Transmissions Work"" Howstuffworks "Auto" HowStuffWorks.com, 1 Apr. 2000. Web. 05 Feb. 2010.
Chicago. Commercial Trades Institute. Auto Transmissions. New York: McGraw-Hill, 1955. Print.
Laspina, Marc. "Auto-Tech - Best of: Manual vs. Automatic Transmissions: Which Is Best." Auto Insurance Quote: Car & Motorcycle Insurance - Progressive. Progressive.com, 14 Mar. 2008. Web. 15 Feb. 2010.
Lydia, Lovric. "LEARNING TO DRIVE A STICK SHIFT BECOMES SECOND NATURE -- FINALLY." Hamilton Spectator, The (ON) n.d.: Newspaper Source Plus. EBSCO. Web. 26 Apr. 2010.
Nice, Karim. "How Torque Converters Work." 25 October 2000. HowStuffWorks.com.
Nice, Karim, and Charles W. Bryant. "How Clutches Work." 16 October 2007. HowStuffWorks.com.
Nice, Karim. "How Automatic Transmissions Work." 29 November 2000. HowStuffWorks.com.
Schultz, Mort. "Drivetrain: A Century of Progress." Popular MechanicsNov. 1985: 38-40,44,46. Print.
"Fuel Economy Test Manual vs Automatic Transmission." Consumer Reports: Expert Product Reviews and Product Ratings from Our Test Labs. ConsumerReports.org, Sept. 2008. Web. 16 Apr. 2010.


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