- The letter A = Aisin-Warner Automatic. Two or three digits. Older transmissions have two digits. The first digit represents the generation (not the number of gears, see A10 vs A20 and A30 vs A40 vs A40D).
- Feb 11, 2021 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 of the parts.
- The 5-speed 5L40-E automatic transmission manufactured by GM was designed for engines with the capacity from 1,8 up to 3,6 liters and the maximum torque equal to 340 Nm. It had been produced from 1998 until 2007. Initially this automatic transmission was intended for cars with longitudinally positioned engine and the rear-wheel drive (RWD).
- Automatic Transmission Gears Explained
- Automatic Transmission Gears Not Engaging
- How A Automatic Transmission Work
- Automatic Transmission Gears Explained
Automatic Transmission Gears Explained
How an Automatic Transmission Shifts Gears. There are three systems within an automatic transmission: electrical, hydraulic, and mechanical. These systems have to work together in order for the transmission to work properly. The electrical system monitors gear selection and speed, along with the position of the throttle. A hydraulic control unit sends hydraulic signals to change gears (via band brakes and clutches) and to lock the torque converter. Note that most modern automatic transmissions use a Ravigneaux.
While your vehicle’s engine may create the inertia to move forward, the transmission determines the speed based on the driver’s desire and sends the power to the wheels to maintain or increase the speed. When things are working well, you should rarely notice the transition between gears in an automatic, especially if the transmission happens to be a CVT.
When the transmission jerks between gears or the transmission is shifting hard, it should be taken as a warning that your transmission needs repair. When a transmission is shifting hard or slipping it’s time for an inspection. An inspection by an expert will tell you whether a simple fix can address the issue or major repairs are due.
Many symptoms exist that indicate the transmission is not operating as well as it should. The most common symptoms of transmission problems include:
1. Slipping Transmission
Slipping occurs when the transmission slips from one gear to the next, instead of gliding smoothly as it should. Transmission slipping can occur in one or several ways including:
- Interruption in acceleration
- Delay or failure to go into reverse
- Extremely high RPMs
- Check engine light on
- Burnt smells
- Difficulty shifting gears
- Shifting accompanied by strange sounds
Causes of transmission slips include:
- Low or Burnt Transmission Fluid – Low fluid can result in overheating and a deficiency in the creation of hydraulic pressure that is needed to engage gears. Fluid levels should be checked often either by you or a technician. Because the transmission is a sealed system, fluid loss is usually related to a leak. Burnt fluid can be compared to the smell of burnt toast and appears burnt as well. Burnt fluid is caused by an overheated transmission or a lack of maintenance which is a bad sign. Once the fluid is burnt, it may already be too late–the transmission may already be damaged.
- Faulty Clutch – Both manual and automatic transmissions use a series of clutches that aid in changing gears. Automatic transmissions are equipped with clutches in the torque converter that lock up at high speeds to prevent slipping, as well as in other areas throughout the transmission that can wear or burn out due to a lack of transmission fluid.
- Worn Out Gears or Transmission Bands – With use and time, it’s possible for gears to wear out. When gears don’t properly fit together, they can create a jerky shifting experience. Similarly, transmission bands that are linked to the gears, in automatic transmissions, can wear down or break over time and require replacement.
- Difficulty with the Torque Converter – A torque converter receives the power from the engine and converts it into torque that the transmission uses to send to the wheels. Over time the converters can wear down, preventing the flow of fluid, which results in slipping among other problems.
- Failed Solenoid – The solenoid is an electro-hydraulic valve that controls the flow of fluid throughout the transmission. Damage or failure to this component can cause the release of too much or too little fluid into the system.
2. Rough Shifting or Jerking Transmission
A car that is experiencing rough shifting may have trouble accelerating, struggle to change gears, or lack a smooth transition. Rough shifting is often described as a clunk or a thud feeling when the vehicle shifts from one gear to the next.
Causes of rough shifting include:
- Transmission Fluid Low or Poor Condition – Vehicles low on transmission fluid or that are operating with worn out or contaminated fluid are likely to experience hard shift conditions. Lack of adequate lubrication within the transmission can cause several problems, including hard shifting. The fluid in your transmission should appear clean, light red in color, and somewhat transparent.
- Vacuum Troubles – On older vehicles, the transmission would know when to shift based on the assistance of a vacuum modulator valve. The valve determines the load of the engine via a hose, called the vacuum line, that connects to the intake, measuring the amount of vacuum within the engine. A bent, blocked, or detached vacuum line can alter the pressure in the transmission producing a rough shift.
- Faulty Sensor – Many vehicles today are equipped with loads of sensors that communicate to their internal computers, including some that influence the transmission to shift. If the sensors are not functioning properly or receiving the incorrect data, it can cause rough shifting. In some cases hard shifting could be caused by a sensor transmitting the wrong data from the engine. A failed speed sensor may signal that the vehicle is traveling at a higher or lower speed than it truly is.
3. Delayed Engagement (Delayed Gear Shift)
Delayed engagement is defined as the pause or delay in response that it takes from shifting from Park into a moving gear such as Reverse or Drive. The duration of the delay can be as quick as a few seconds and up to one minute. Delayed engagement should not be ignored and is a warning sign that your transmission needs attention sooner rather than later.
Causes of delayed engagement include:
- Low transmission fluid
- Poor fluid maintenance
- Failed transmission solenoids
Transmission Troubles
Slipping, rough shifting, and delayed engagement troubles are often due to poor condition or lack of transmission fluid; that’s why it is so important to have the condition of your fluid checked and flushed every 30,000 – 50,000 miles.
If you experience any of the above symptoms while driving your vehicle and it’s accompanied by the Check Engine Light, have the vehicle inspected immediately. Ignoring the light could result in costly repairs that could have otherwise been avoided.
D3 (or 3)
As the name suggests, the D3 (or sometimes just 3) mode will only utilize the first 3 gear ratios of your car, or in some, locks it on the 3rd gear only. Just like the 2 and L, it will shift at a higher gear if the maximum RPM has been reached. It will also maximize the RPM range per gear for the needed power and pull.
Automatic Transmission Gears Not Engaging
Where to use?
Since this limits the car up to the third gear only, the speed will also be limited for cruising. This is useful especially when towing a trailer or another car since you have to control your speed. You can also use this during heavy rainfall where slowing down is highly recommended. For other do’s and don’ts in driving in the rain, visit the AutoDeal blog.
How A Automatic Transmission Work
Some brands also have the +/- or the M shift mode. This is usually in combination with paddle shifters at the back of the steering wheel; an up and down option on the gear shifter; or a +/- switch on the shifter knob. You can use this to downshift or upshift manually in certain situations without getting out of the automatic transmission capability. For example, when overtaking, it’s recommended that you downshift in order to get the needed power. You can do this with the +/- mode.
Automatic Transmission Gears Explained
These are the most common modes you could see in cars today. Others may have more but that can be car specific so you can refer to your owner’s manual for instructions. With proper use of these driving modes, you will be able to maximize the use of your car even when it has an automatic transmission.