Category: How Automatic Transmissions Work

Next to the cost of replacing an engine, replacing a transmission is the most expensive vehicle repair an owner can make. Expect to pay between 1,000 and 10,000 for completely replacing a transmission. Having the original transmission repair (rebuilding the transmission) is even pricier,  depending on the extent of the damage and make of the vehicle….

Giving small time and small amount for your vehicle to go on a Preventive Maintenance will prevent you to spend in high amount of repair and encumbrance. The Automatic Transmission is one of the most expensive and precious to repair. To maintain your Automatic Transmission in good condition, prevent repair and high expenses, here are some…

Just like that of a manual transmission, the automatic transmission’s primary job is to allow the engine to operate in its narrow range of speeds while providing a wide range of output speeds. Without a transmission, cars would be limited to one gear ratio, and that ratio would have to be selected to allow the car to travel…

If you have ever driven a car with an automatic transmission, then you know that there are two big differences between an automatic transmission and a manu­al transmission: There is no clutch pedal in an automatic transmission car. There is no gear shift in an automatic transmission car. Once you put the transmission into drive, everything else…

This automatic transmission uses a set of gears, called a compound planetary gearset, that looks like a single planetary gearset but actually behaves like two planetary gearsets combined. It has one ring gear that is always the output of the transmission, but it has two sun gears and two sets of planets. Let’s look at some…

This transmission does something really neat in order to get the ratio needed for second gear. It acts like two planetary gearsets connected to each other with a common planet carrier. The first stage of the planet carrier actually uses the larger sun gear as the ring gear. So the first stage consists of the…

By definition, an overdrive has a faster output speed than input speed. It’s a speed increase — the opposite of a reduction. In this transmission, engaging the overdrive accomplishes two things at once. If you read How Torque Converters Work, you learned about lockup torque converters. In order to improve efficiency, some cars have a mechanism…

When you take apart and look inside an automatic transmission, you find a huge assortment of parts in a fairly small space. Among other things, you see: An ingenious planetary gearset A set of bands to lock parts of a gearset A set of three wet-plate clutches to lock other parts of the gearset An…

Reverse is very similar to first gear, except that instead of the small sun gear being driven by the torque converter turbine, the bigger sun gear is driven, and the small one freewheels in the opposite direction. The planet carrier is held by the reverse band to the housing. So, according to our equations from…

One of the planetary gearsets from our transmission has a ring gear with 72 teeth and a sun gear with 30 teeth. We can get lots of different gear ratios out of this gearset. Input Output Stationary Calculation Gear Ratio A Sun (S) Planet Carrier (C) Ring (R) 1 + R/S 3.4:1 B Planet Carrier…

Most automatic transmissions have a 1:1 ratio in third gear. You’ll remember from the previous section that all we have to do to get a 1:1 output is lock together any two of the three parts of the planetary gear. With the arrangement in this gearset it is even easier — all we have to…

To shift properly, the automatic transmission has to know how hard the engine is working. There are two different ways that this is done. Some cars have a simple cable linkage connected to a throttle valve in the transmission. The further the gas pedal is pressed, the more pressure is put on the throttle valve. Other cars…

Hydraulics The automatic transmission in your car has to do numerous tasks. You may not realize how many different ways it operates. For instance, here are some of the features of an automatic transmission: If the car is in overdrive (on a four-speed transmission), the transmission will automatically select the gear based on vehicle speed…

If you prefer or own an automatic, here are 5 tips that you should be aware of while driving on the road. Engage P only when you’ve come to a complete stop When driving an automatic, always remember that you should engage the gear stick to P (Park) only when your vehicle comes to a…

An automatic transmission with a manual mode allows the driver to shift gears without a clutch pedal. Electronically controlled transmissions, which appear on some newer cars, still use hydraulics to actuate the clutches and bands, but each hydraulic circuit is controlled by an electric solenoid. This simplifies the plumbing on the transmission and allows for…