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What is the Difference between Automatic and Manual Transmissions?

Skilled drivers can shift a manual transmission faster than an automatic.
A woman shifting gears with a manual transmission.
Cutaway view of a transmission.
A transmission without the housing.
A clutch, part of a transmission.
Both automatic and manual transmissions are made from a series of gears.
A manual transmission may be found in off-road vehicles.
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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 28 September 2014
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Automatic and manual transmissions are both used to change a vehicle's gear ratio so that it can perform more effectively and efficiently. These systems work in very similar ways, with the primary difference between these two transmissions being the way in which the driver interacts with them. In addition to these two basic styles, it is also possible to find a semi-automatic transmission, which blends elements of both.

Cars need to change gear ratios to work properly. If a car is driven with a low gear ratio, it can only effectively function at low speeds, and acceleration would cause the engine to “redline,” or reach the point beyond which it cannot operate very well. High gear ratios are needed for high speeds, but a car can't be driven at a high gear ratio when it is going slowly. Hence, transmissions are needed to allow the gear ratio to be changed as needed.

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In the case of a manual transmission, the driver of the car must change gears as he or she perceives a need to do so. Drivers rely on cues like the driving conditions and the tachometer to determine the best moment to change gears, and they change gears by engaging the clutch pedal, causing the gears in the car to disengage, and moving the gear shift to select a new gear ratio before disengaging the clutch so that the gears will re-engage. As all drivers who have learned to drive a car with a manual transmission know, this procedure can be challenging, and the learning curve on manual transmissions can be steep and very frustrating.

A car with an automatic transmission selects the correct gear for the driver, using a complex communications system which incorporates information about the speed of the car, whether the driver is accelerating or braking, and the revolutions per minute (RPM) of the engine. All of this work is done without the driver's participation: to go forward, the driver uses a lever to put the car in “drive,” and to go in reverse, the driver uses the “reverse” option. Automatics usually also have a “park” and “neutral” option, and some have overdrive for high speeds, along with low gears for special driving conditions like snow.

Semi-automatic transmissions blend these two systems. The driver is allowed to select the gear, as with a manual transmission, but gear selection is accomplished with a lever like that used in an automatic transmission. No clutch is involved, and the car will usually switch gears for the driver if he or she fails to do so and the engine appears to be in danger.

From the point of view of the driver, an automatic transmission is much easier to drive. It also requires more serious repairs if it fails, however, and a manual transmission tends to be more gas-efficient when driven by an experienced driver. Drivers who like to get more performance out of their cars may also prefer to work with a manual transmission.

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BrickBack
Post 2

Oasis11-You really have to know how to operate the car and it could take a while to get used to.

Manual transmission is often used with old sports cars. People that love old sports cars usually like to shift the gears themselves and enjoy the feel of the road.

It really adds excitement when driving these cars. Also with manual transmission, the passengers in the car feel the changes in gears while with the automatic transmissions the ride is smoother.

Manual transmissions tend to have more gear problems because you can incorrectly ride out the gears.

Transmission repair is costly. If you find that your speed will not go above a certain speed regardless of your effort then you have transmission problems.

Replacing a transmission with a new transmission is expensive and can run you several thousand dollars. Perhaps a rebuilt transmission might be more cost effective especially if it is a car that is old.

oasis11
Post 1

Automatic transmission is what most cars currently have. This used to be a premium or an extra charge added to the cost of a vehicle, but most consumers have come to expect that most vehicles will come with this type of automotive transmission.

It is really easy as all of the gears are labeled. For example the P stands for Park while the R is for reverse and the D is for drive.

However a car with manual transmissions requires the person driving to know how to shift into different gears without the help of any labeling.

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