Automatic transmissions are amazing works of engineering because they let you change gears smoothly and drive without any problems. When they don’t shift properly, though, it can be annoying and even dangerous.
It would be awful to be driving down the highway and find that your car is stuck in one gear. It’s annoying, right? An automatic gearbox is a great example of modern tech because it changes gears smoothly, making the ride smooth. But what happens when this very well-tuned machine stops working? This detailed guide goes into great detail about automatic transmissions, which will help you figure out common problems and get your car back on the road.
What is an Automatic Transmission?
An automatic gearbox is a complicated piece of machinery that changes gears for you without you having to do it by hand. It has many parts, like gears, clutches, bands, valves, and a torque converter, which all work together to send power from the engine to the wheels.
Automatic transmissions are like silent conductors, coordinating gear changes for best performance. This is in contrast to manual transmissions, which require the driver to control the clutch and choose the gear. In simpler terms, here’s what it means:
- Torque Converter: This important part moves power from the engine to the gearbox easily, like a fluid coupling.
- Planetary Gear Set: This complicated set of gears has different gear ratios for speeding up, slowing down, and stopping the engine.
- Hydraulic System: This system of tubes and valves uses automatic gearbox fluid (ATF) to manage which gears are engaged based on the load and speed of the engine.
- Transmission Control Module (TCM): This computer brain gets information from different sensors and manages gear changes by controlling the hydraulic system.
Key Parts and Their Functions
The most important parts of your automated gearbox are:
- Solenoids are electronic switches that control the flow of fluid in the hydraulic system by engaging certain gear sets.
- Governor: This part keeps an eye on the engine’s speed and changes the hydraulic pressure to make sure that shifting goes smoothly at higher RPMs.
- Sensors: The input and output shafts have speed sensors, and the control position sensor gives the TCM important information for choosing the best gear.
Symptoms of Failing Components
Torque Converter: If the engine shakes when accelerating, gets too hot, or doesn’t produce power, this could be a sign of a broken torque converter.
- Planetary Gearset: Grinding sounds, trouble activating certain gears, or the loss of all gears could be signs of worn-out gear components.
- Valve Body: Shifting that doesn’t work right, changes gears slowly, or doesn’t work at all could be signs of a broken valve body.
- Solenoids: When solenoids don’t work right, they can cause symptoms that are similar to those of a broken valve body.
- TCM: The TCM can be the cause of strange behaviour, a lit check engine light, and shifting problems.
Common Types and Their Applications
- Conventional Automatic Transmission (CAT): This is the most popular type. It changes gears with hydraulic pressure and a governor. Often found in older cars and some newer, more fuel-efficient cars.
- Continuously Variable Transmission (CVT): This type of transmission uses a belt or chain system to change gear ratios easily, which saves a lot of gas. Used a lot in hybrids and smaller cars.
- The Dual-Clutch Transmission (DCT) is like an automatic transmission but works like a manual transmission. It has two clutches that are used to choose gears ahead of time, which makes shifting very fast. This is popular in high-performance cars.
Different Types of Automatic Transmission Fluid (ATF):
- These ATFs, Dexron and Mercon, are used in a lot of cars in the US and Asia. There are different Dexron/Mercon specifications, such as Dexron III, VI, and Mercon V. It is very important to use the ATF that the maker recommends for your car.
- Universal ATFs: Some companies sell universal ATFs that they say can work with a number of gears. Even though these are handy, they might not work or protect your gearbox as well as they should.
- CVT Fluids: Fluids made just for continuously variable transmissions are needed to make sure they work right and keep them from wearing out.
How to Approach an Automatic Transmission Not Shifting
A full fix might need to be done by a professional, but here’s a basic way to troubleshoot:
- The ATF level and condition should be checked. The fluid shouldn’t be burned or dirty, and the ATF level should be right. A simple drain and refill could fix small moving problems.
- Check for Error Codes: These days, cars have trouble codes that can help you figure out what’s wrong. A code reader can give you important hints.
- Talk to a mechanic: For complicated problems or possible internal damage, it’s important to find a skilled mechanic who can properly diagnose and fix the problem.
Beyond the Basics: Advanced Troubleshooting
For workers with more experience, the next steps in troubleshooting are:
- Solenoid Testing: An electrical problem can be found by using a scan tool or voltmeter to check how the solenoid works.
- Hydraulic Pressure Testing: Checking the hydraulic pressure inside the gearbox can help find problems with the valves, pumps, or leaks inside the gearbox.
- Transmission Rebuild: In severe cases, it may be necessary to do a full transmission rebuild to repair worn-out parts and get the car working again.
