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Advantages of Automatic Transmissions

Sun, 28 Feb 2010 16:44:40 +0000

Even though now manual transmissions are more popular than automatic transmissions, the latter ones have become important competitors of the former transmissions, even in the case of cheap cars. When a car owner chooses the fuel, he or she thinks of its advantages and disadvantages. They also consider in the same manner, concerning pros and cons, the transmission type.

Mechanic transmissions are based on fixed axes, with two or three axles and with cylindrical gear wheels, of steep teeth (lifting power in this case is high and there is low noise level on the move, even in the case of cheap cars).

Automatic transmissions are of three types. The first type is based on a hydro transformer and planet gear, and the second type has a chained mechanic variation device with planet gear, for expensive cars like Audi, but also for cheap cars. The third type is special and it is equipped with double coupler and cylindrical gear provided by BMW or Mercedes.

According to experts, one Audi car out of four is equipped with automatic transmissions. In the case of many cheap cars, mechanic transmissions are more dynamic, effective and they are not associated with high fuel consumption because there are no automation elements involved. Two disadvantages of these transmissions are lower comfort and power flow interruption while changing speed level.

On the other hand, automatic transmissions are characterized by a high degree of comfort and speed level changes without interrupting power flow. Another advantage of these transmissions is less considerable transmission shock during coupling or decoupling speed level.

There are cases when this transmission can almost reach the ideal feature at the traction level: maximum wheel power regardless the speed, which means very good dynamic and economic features, through the continuous variation of the speed ratio. The good news in these cases is that it can be associated with engines of at least 200 horsepower and 300 Newton-meters, instead of less powerful engines.

Automatic transmissions can be in general effective, in spite of higher fuel consumption, less dynamism and higher costs. Nevertheless, an automatic transmission is able to combine successfully the advantages of both transmissions types. It is remarkable through its sporty features, as it is very dynamic, it is effective, and the consumption is almost similar to a manual transmission. Besides, comfort is high and speed can be changed without interrupting power flow.

Obviously, the car of our dreams has automatic transmission, it is cheap, and it meets all the pollution standards. It is comfortable and environmentally friendly. Besides, there are perspectives to replace the traditional fuel with alternative versions. In addition, automatic transmission is a feature of many luxury cars nowadays.

However, cheaper cars can also be equipped with such transmission and they can be sold at accessible prices. Automatic transmission is recommended for big cities where traffic is intense and there are quite frequent traffic jams. If you are fond of cars and you want to know more details about transmissions, first you have to know that their technology differs from a producer to another.

Manual Vs. Automatic Transmission: Which Vehicle Should You Choose?

Sun, 28 Feb 2010 16:44:36 +0000

While manual cars are not as popular as they used to be (owing to the rising demand for automatic cars especially in the Americas and Europe), they still account for a substantial percentage of annual car sales (both used and new). Perhaps the reason for this is the advantages of a manual transmission over an automatic, which are as follows:

Manual Transmission

Lower base price, repair, and maintenance costs. Manual vehicles generally have a lower base price than automatics. On the average, a manual costs $1000 dollars lesser than an automatic. When it comes to repair and maintenance costs, manual transmission appears to be more superior. The clutch, which is one of the most expensive and labor intensive components of a car when it gets damaged, is more easily maintained in manual than in automatic transmission. And any mechanic can tell you that working on a manual transmission is much easier than working with automatic gear boxes. So the repair costs for automatics are significantly higher. In the long run, manuals require less service, thus making maintenance cheaper.

Gives higher gas mileage. Even if a manual car is relatively more difficult to drive, it doesn’t eat up too much fuel, consuming 5%-15% lesser fuel depending on road conditions and driving habits. Automatics, even though easier to use, ultimately burn a lot more gas than their manual counterparts.

Gives better control. The basic premise is that manual transmission allows for better control of the car. With a manual, you can keep the power of the engine right where you want it, based on the conditions of the road. And no matter how sophisticated the electronics, automatic transmission will never be smarter than the human brain that’s actually driving the car. Simply put, manual transmission gives you full control with your gears but with an automatic your choices are limited between two pedals. Manual transmission gives you more freedom when it comes to maneuvering on steep hills or curves. It also allows you to combat tough weather conditions more comfortably.

With all these advantages of a manual transmission notwithstanding, here are the reasons why automatics have been very popular nowadays:

Automatic Transmission

Ease of use. Generally, automatic transmissions are easier to operate. There are only two pedals, so it’s almost like driving a go-kart. In a traffic jam, this is a big plus. Manuals are generally more tiring to drive in traffic, because of the need to use the clutch pedal.

Relatively safer. When driving an automatic, a driver will have his/her left foot free and both hands on the wheel. A manual requires a little too much concentration from the driver: the continuous pumping of the clutch pedal and the constant shifting of gears is enough to distract a novice driver.

The best of both worlds. With new options like manumatic transmissions, automatics may finally be gaining on manuals, combining ease of use with power. At the onset of the 21st century, this new transmission mode was introduced by automobile manufacturers. Manumatic transmission is basically an automatic transmission that possesses certain manual-transmission features. A good example is the luxury cars of Chrysler. It’s definitely automatic, only that you have more control in shifting your gears.

Conclusion:
In the end, your decision shouldn’t be based only on the advantages and disadvantages. It ultimately boils down on your needs. For example, if you want maximum performance and superior control, you may want to consider getting a manual transmission. If you want ease of driving, especially in heavy traffic, automatic transmission is your best choice.

Cars With Automatic Transmission Are Here To Stay

Sun, 28 Feb 2010 10:44:30 +0000

Cars with automatic transmission are gaining ground in the India. Hardly a few people had heard of automatic transmission in cars a few years ago. Unlike the West, the car drivers here were fond of manual transmission more and to meet their requirements the Indian car market here was full of cars with manual transmission system. People wanted to feel the pleasure of driving and thus stayed away from buying cars with automatic transmission.

While driving, an automatic transmission system in a car does not require a driver’s intervention. The driver just needs to only use the acceleration and brake pedals, and can enjoy the drive without changing the gears. Interestingly, 95% of car buyers in the United States go for cars that have automatic transmission. However, it did not appeal to customers for long here. Now those days are gone. The cars with automatic transmission are gaining popularity, particularly among the women.

Basically the concept of automatic transmission in cars is still new to India. In fact, the cars with automatic transmission are different from those with manual transmission in terms of power, acceleration, fuel economy, and driving comfort. Women are feeling they are easy is to drive and are buying such cars especially in urban areas. Consequently, the demand for such cars has gone up and the car manufacturers are launching the automatic variants of their models.

Women are finding automatic transmission good because of its smooth shifting capabilities. The occupants enjoy a jerk-free ride and the fuel economy of the car also sees an improvement. Some customers are even go for both manual and automatic switch options.

Some of the cars with automatic transmission that are popular in the country are as follows:

Mahindra & Mahindra launched the automatic version of Scorpio in 2008. The Scorpio AT comes with a complete 6-speed automatic gearbox and the powerful 2.2 litre mHawk engine. Being a flagship model of Mahindra & Mahindra, the Scorpio is also the first sport utility vehicle (SUV) to be equipped with a 6-speed automatic transmission in the country.

Leading Japanese car maker Honda is released its variants with automatic transmissions Civic, Accord, City and the CR-V to the Indian market and they are being widely well received by the customers here.

American auto major General Motors is offering a four-speed automatic gearbox option for the Chevrolet Optra. Its Captiva LTZ comes with a five-speed automatic transmission.

Hyundai’s small car Santro Xing comes with automatic transmission and an H-matic four-speed automatic transmission is available in the Sonata 2.7 V6 variant.

Maruti Udyog’s Wagon R and the Esteem also feature a three-speed automatic transmission system.

As a special offer on the occasion of International Women’s Day, Hyundai released the automatic version of the Santro. It was a limited version which witnessed huge sales and thus Hyundai was able to find out the target customers for its automatic models.

Hyundai’s i20, Chevrolet Captiva (AT version), Fiat’s Linea, Honda City, Mitsubishi Outlander, Mahindra Scorpio and Mitsubishi Outlander are the other models that feature automatic transmission.

The Hyundai i10 has been one of the most popular cars with automatic transmission. It received a great response from women. Other than i10, Verna from the sedan segment also comes with automatic transmission.

Encouraged by the growing demand for such cars, the car manufacturers are now offering five to six speed automatic transmission systems which deliver better fuel-efficiency clubbed with improved pick up and performance. All these things indicate that the trend of automatic transmission cars is here to stay and have proved the notions of many people who have predicted that such cars will not be a success here.

Transmission repairs

Thu, 12 Nov 2009 21:21:18 +0000

There are several problems that can be resolved with an adjustment (A simple adjustment is one that can be made without removing the transmission from the vehicle.) or minor repair.
If a late model transmission (computer-controlled transmissions started becoming popular in the early ’90s) is not shifting properly, it is often the result of a computer sending incorrect signals due to a faulty sensor, or the transmission is not reacting to the computer command because of a bad connection or defective solenoid pack. These problems can be corrected while the transmission is in the car for considerably less money then a complete overhaul.

If a non computer-controlled transmission is shifting too early or too late, it may require an adjustment to the throttle cable. Since throttle cables rarely go out of adjustment on their own or due to wear and tear, these mis-adjustments are usually due to other repair work or damage from an accident. If the vehicle has a vacuum modulator instead of a throttle cable, there is an adjustment that can be made using an adjustment screw in some modulator designs. In vehicles with modulators, however, it is very important that there are no vacuum leaks and the engine is running at peak efficiency. Engine vacuum is very sensitive to how well the engine is running. In fact, many technicians use a vacuum gauge to diagnose performance problems and state-of-tune. Many problems that seem to be transmission problems disappear after a tune-up or engine performance related repair was completed.

In some older transmissions, bands can be adjusted to resolve “slipping” conditions. Slipping is when an engine races briefly when the transmission shifts from one gear to the next. There are no adjustments for clutch packs however.
Reseal job
A transmission is resealed in order to repair external transmission fluid leaks. If you see spots of red oil on the ground under the car, your transmission may be a candidate for a reseal job. In order to check a transmission for leaks, a technician will put the car on a lift and examine the unit for signs of oil leaks. If a leak is spotted at any of the external seals or gaskets and the transmission otherwise performs well, the technician will most likely recommend that the transmission be resealed.
Most of the external seals can be replaced while the transmission is still in the car but, if the front seal must be replaced, the transmission must first be removed from the vehicle in order to gain access to it, making it a much costlier job.
Replace accessible parts
There are a number of parts that are accessible without requiring the removal of the complete transmission. many of the control parts including most of the electrical parts are serviceable by simply removing the oil pan. The parts that are accessible, however, vary from transmission to transmission and most transmission repair facilities would hesitate to provide meaningful warrantees on external repairs for the simple reason that they cannot see if there are any additional internal problems in the components that are only accessible by transmission removal.
Complete Overhaul
In a complete overhaul (also known as rebuilding a transmission), the transmission is removed from the vehicle and completely disassembled with the parts laid out on a workbench. Each part is inspected for wear and damage and then either cleaned in a special cleaning solution, or replaced with another part depending on its condition. Parts that have friction surfaces, such as bands and clutches are replaced as are all seals and gaskets. The torque converter is also replaced, usually with a remanufactured one. Technical service bulletins are checked to see if the auto manufacturer recommends any modifications to correct design defects that were discovered after the transmission was built. Automobile manufacturers often make upgrade kits available to transmission shops to resolve these design defects.
Replacement unit vs. overhaul existing unit
When a transmission requires an overhaul, there are generally two options that you may have. The first is to remove your existing transmission and overhaul it, then put the same, newly rebuilt unit back in your car. The second option is to replace your existing unit with another unit that has already been rebuilt or remanufactured.
The second option will get you out of the shop and on your way much faster but may cause you problems down the road. The reason for this is that, in some but not all cases, a particular transmission model can have dozens of variations depending on which model car, which engine, which axle ratio, even which tire size. The problems you could experience could be as simple as a speedometer that reads too high or too low (the speedometer is usually connected by cable to a gear in the transmission output shaft.) You may also experience incorrect shift points or even complete transmission failure because your engine may be more powerful then the one the replacement unit was originally designed for. This is not the case with all transmission models so voice your concerns with your technician. Most shops will rebuild your existing unit if you request it as long as they can afford to have a lift tied up with your car while the transmission is being rebuilt. Of course this is only important if you are sure that the transmission you have is the original one and has never previously been replaced.Experienced engineers with ID lanyards can explain you better about the full process once you are at the sales office.

Torque Converter

Sun, 08 Nov 2009 21:10:04 +0000

On automatic transmissions, the torque converter takes the place of the clutch found on standard shift vehicles. It is there to allow the engine to continue running when the vehicle comes to a stop. The principle behind a torque converter is like taking a fan that is plugged into the wall and blowing air into another fan which is unplugged. If you grab the blade on the unplugged fan, you are able to hold it from turning but as soon as you let go, it will begin to speed up until it comes close to the speed of the powered fan. The difference with a torque converter is that instead of using air, it uses oil or transmission fluid, to be more precise.

A torque converter is a large doughnut shaped device (10″ to 15″ in diameter) that is mounted between the engine and the transmission. It consists of three internal elements that work together to transmit power to the transmission. The three elements of the torque converter are the Pump, the Turbine, and the Stator. The pump is mounted directly to the converter housing which in turn is bolted directly to the engine’s crankshaft and turns at engine speed. The turbine is inside the housing and is connected directly to the input shaft of the transmission providing power to move the vehicle. The stator is mounted to a one-way clutch so that it can spin freely in one direction but not in the other. Each of the three elements have fins mounted in them to precisely direct the flow of oil through the converter

With the engine running, transmission fluid is pulled into the pump section and is pushed outward by centrifugal force until it reaches the turbine section which starts it turning. The fluid continues in a circular motion back towards the center of the turbine where it enters the stator. If the turbine is moving considerably slower than the pump, the fluid will make contact with the front of the stator fins which push the stator into the one way clutch and prevent it from turning. With the stator stopped, the fluid is directed by the stator fins to re-enter the pump at a “helping” angle providing a torque increase. As the speed of the turbine catches up with the pump, the fluid starts hitting the stator blades on the back-side causing the stator to turn in the same direction as the pump and turbine. As the speed increases, all three elements begin to turn at approximately the same speed.

Since the ’80s, in order to improve fuel economy, torque converters have been equipped with a lockup clutch (not shown) which locks the turbine to the pump as the vehicle speed reaches approximately 45 – 50 MPH. This lockup is controlled by computer and usually won’t engage unless the transmission is in 3rd or 4th gear.Use your business checks and upgrade your office automobiles for secure driving.

Planetary Gear Sets

Thu, 05 Nov 2009 21:05:01 +0000

Automatic transmissions contain many gears in various combinations. In a manual transmission, gears slide along shafts as you move the shift lever from one position to another, engaging various sized gears as required in order to provide the correct gear ratio. In an automatic transmission, however, the gears are never physically moved and are always engaged to the same gears. This is accomplished through the use of planetary gear sets.

The basic planetary gear set consists of a sun gear, a ring gear and two or more planet gears, all remaining in constant mesh. The planet gears are connected to each other through a common carrier which allows the gears to spin on shafts called “pinions” which are attached to the carrier .

One example of a way that this system can be used is by connecting the ring gear to the input shaft coming from the engine, connecting the planet carrier to the output shaft, and locking the sun gear so that it can’t move. In this scenario, when we turn the ring gear, the planets will “walk” along the sun gear (which is held stationary) causing the planet carrier to turn the output shaft in the same direction as the input shaft but at a slower speed causing gear reduction (similar to a car in first gear).

If we unlock the sun gear and lock any two elements together, this will cause all three elements to turn at the same speed so that the output shaft will turn at the same rate of speed as the input shaft. This is like a car that is in third or high gear. Another way that we can use a Planetary gear set is by locking the planet carrier from moving, then applying power to the ring gear which will cause the sun gear to turn in the opposite direction giving us reverse gear.

The illustration on the right shows how the simple system described above would look in an actual transmission. The input shaft is connected to the ring gear (Blue), The Output shaft is connected to the planet carrier (Green) which is also connected to a “Multi-disk” clutch pack. The sun gear is connected to a drum (yellow) which is also connected to the other half of the clutch pack. Surrounding the outside of the drum is a band (red) that can be tightened around the drum when required to prevent the drum with the attached sun gear from turning.

The clutch pack is used, in this instance, to lock the planet carrier with the sun gear forcing both to turn at the same speed. If both the clutch pack and the band were released, the system would be in neutral. Turning the input shaft would turn the planet gears against the sun gear, but since nothing is holding the sun gear, it will just spin free and have no effect on the output shaft. To place the unit in first gear, the band is applied to hold the sun gear from moving. To shift from first to high gear, the band is released and the clutch is applied causing the output shaft to turn at the same speed as the input shaft.

Many more combinations are possible using two or more planetary sets connected in various ways to provide the different forward speeds and reverse that are found in modern automatic transmissions.

Some of the clever gear arrangements found in four and now, five, six and even seven and eight-speed automatics are complex enough to make a technically astute lay person’s head spin trying to understand the flow of power through the transmission as it shifts from first gear through top gear while the vehicle accelerates to highway speed. On modern vehicles (mid ’80s to the present), the vehicle’s computer monitors and controls these shifts so that they are almost imperceptible.

Clutch Packs

A clutch pack consists of alternating disks that fit inside a clutch drum. Half of the disks are steel and have splines that fit into groves on the inside of the drum. The other half have a friction material bonded to their surface and have splines on the inside edge that fit groves on the outer surface of the adjoining hub. There is a piston inside the drum that is activated by oil pressure at the appropriate time to squeeze the clutch pack together so that the two components become locked and turn as one.

What is a transmission?

Mon, 02 Nov 2009 20:56:01 +0000

The transmission is a device that is connected to the back of the engine and sends the power from the engine to the drive wheels. An automobile engine runs at its best at a certain RPM (Revolutions Per Minute) range and it is the transmission’s job to make sure that the power is delivered to the wheels while keeping the engine within that range. It does this through various gear combinations. In first gear, the engine turns much faster in relation to the drive wheels, while in high gear the engine is loafing even though the car may be going in excess of 70 MPH. In addition to the various forward gears, a transmission also has a neutral position which disconnects the engine from the drive wheels, and reverse, which causes the drive wheels to turn in the opposite direction allowing you to back up. Finally, there is the Park position. In this position, a latch mechanism (not unlike a deadbolt lock on a door) is inserted into a slot in the output shaft to lock the drive wheels and keep them from turning, thereby preventing the vehicle from rolling.

There are two basic types of automatic transmissions based on whether the vehicle is rear wheel drive or front wheel drive.

On a rear wheel drive car, the transmission is usually mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position. A drive shaft connects the rear of the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheels. Power flow on this system is simple and straight forward going from the engine, through the torque converter, then through the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear wheels.

On a front wheel drive car, the transmission is usually combined with the final drive to form what is called a transaxle. The engine on a front wheel drive car is usually mounted sideways in the car with the transaxle tucked under it on the side of the engine facing the rear of the car. Front axles are connected directly to the transaxle and provide power to the front wheels. In this example, power flows from the engine, through the torque converter to a large chain that sends the power through a 180 degree turn to the transmission that is along side the engine. From there, the power is routed through the transmission to the final drive where it is split and sent to the two front wheels through the drive axles.

There are a number of other arrangements including front drive vehicles where the engine is mounted front to back instead of sideways and there are other systems that drive all four wheels but the two systems described here are by far the most popular. A much less popular rear drive arrangement has the transmission mounted directly to the final drive at the rear and is connected by a drive shaft to the torque converter which is still mounted on the engine. This system is found on the new Corvette and is used in order to balance the weight evenly between the front and rear wheels for improved performance and handling. Another rear drive system mounts everything, the engine, transmission and final drive in the rear. This rear engine arrangement is popular on the Porsche.

Angular momentum

Sun, 06 Sep 2009 16:36:31 +0000

What important to car speed is moment of inertia. Since automotive use circular shapes for lots of engine parts. Therefore angular momentum is vital element. Moment of inertia, with respect to rotation, is called angular momentum. Angular momentum is the force that has to be overcome to spin a circular component (e.g., a flywheel and clutch). It is the function of the mass of the part and the radius on which the mass is positioned. The more centered the mass is on a circular part, the lower the angular momentum, and the less horsepower is needed to spin the part. This translates to the flywheel/clutch assembly being able to accelerate faster at every rpm range.

For example, Quarter Master ís aluminum flywheel and 7-1/4″ aluminum clutch unit together are rated at 146.3 inch-pounds. In other words, the assembly requires approximately 146.3 inch-pounds of force to initiate movement.QMís aluminum flywheel and the new compact 5-1/2″ aluminum clutch unit require approximately 101 inch-pounds of force to initiate movement (a 30% reduction).

This kind of information is easily found on the internet. Check this link out and you will get more useful information for your car . http://www.a1articles.com/index_1_31.html