The Anatomy of Healthy Cars: A Service and Repair Blog

How To Diagnose The Automatic Transmission System Of Your Car

by Brittany Marshall

Of the thousands of parts in car, one part that a car can't do without is the transmission system. The transmission system of a car is the system responsible for transmitting power from the engine to the wheels of the car. Basically, it comprises of a gear system, a shaft, and axles. In a manual transmission, the driver is responsible for setting and changing the gears. In automatic transmissions, though, the system changes the gear by itself; it is like a system that works behind the scenes. This renders the design of an automatic transmission a complex one and one that makes it harder to detect faults and make repairs. With the help of a few tips, though, you can find it a bit easier.

The Transmission Is Not Shifting Or It Delays In Shifting

Most automatic transmission cars use a powertrain control module (PCM), a form of microprocessor that controls the transmission function of the engine.  In other words, it is accountable for all shift timing characteristics. For the PMC to make a well-timed shift, it must get the correct speed readings from the vehicle speed sensor, which is a device that measures the speed of the vehicle. If the speed sensor fails, the vehicle PMC will have no input readings, and hence, it will not shift the transmission gears properly.

To ensure that the sensor is working accordingly, check and confirm that the speedometer -- a gauge that measures and displays how fast your car is moving -- is also working correctly. If it is not working properly, you need to replace the vehicle speed sensor. It is better to contact a professional for such a task.

The Transmission Fades In And Out Of Gear

If you are experiencing problems with the transmission fading in and out of gear, especially when you are moving around corners or when our vehicle is cold, it implies that the transmission fluid is low. To check if that is the case, park your car on a flat ground and ensure the engine is in idling state. Then locate your vehicle's transmission fluid dipstick; it is usually placed which is usually placed where the rear of the engine meets the transmission.

Wipe the dipstick and insert it in the fluid. The dipstick is supposed to have two markings – one for cold and one for warm. If the fluid does not rise up to the warm line, you have to add more of the fluid. Add the transmission fluid slowly and check after short intervals of time if the fluid level has risen to the warm line.