There are many factors that work together to ensure that your vehicle performs as it should. An essential element is the automatic transmission, which transmits the engine’s power to the wheels. If the car won’t shift in any gear with an automatic transmission, you have some problems to deal with.
In this guide, we take a look at the reasons why you can’t get your car to move. We also give you some tips on how to fix it and get back on the road.
Reasons why the car does not move in any gear (automatic transmission)
The most common reason is a low transmission fluid level or a leak. Otherwise, the car may not move due to a clogged filter, faulty valve body, faulty shift solenoid, faulty torque converter, faulty throttle position sensor speed, etc., a faulty transmission control unit, or worn clutches.
Here is a more detailed list of reasons why your automatic transmission cannot shift gears:
1. Lack of transmission fluid
One of the most common reasons for transmission problems is low transmission fluid. Transmission fluid is needed to maintain gear shifting and keep the car moving forward.
There may be a transmission fluid leak that needs to be addressed. You can check the fluid level on the transmission fluid dipstick and top it off if necessary. Additionally, you want to repair transmission leaks before allowing permanent damage to the transmission. In some ways, this would be the easiest and cheapest solution to your car problems.
RELATED: 6 Symptoms of Low Transmission Fluid Level (Check Level)
2. Clogged transmission filter
The transmission also contains a filter responsible for preventing harmful contaminants and dust from causing damage. If you don’t change the filter during your regular maintenance, you are allowing debris to build up inside. Eventually, this practice will lead to a clogged transmission filter.
When the filter becomes clogged, you may hear a hissing sound. As the condition worsens, you may be able to drive sporadically before it stops again. Generally, you should replace the transmission filter every 30,000 miles or every two years, whichever comes first. But check your owner’s manual for the correct intervals for your vehicle.
If you haven’t done this recently and are having transmission problems, this is a good place to start. You can also replace the fluid at the same time, which helps keep your transmission in top condition. Fortunately, changing transmission fluid doesn’t cost much.
READ MORE: How Much Does a Transmission Fluid Change Cost?
3. Defective shift solenoid or valve body
The transmission valve body contains hydraulic channels through which fluid flows when the shift solenoids operate. Shift solenoids can deteriorate over time and the valve body channels can become clogged when the transmission fluid becomes dirty. As the valve body deteriorates, you will begin to notice vibrations when shifting gears. The car can also stop. Once it’s bad enough, the vehicle won’t move at all.
Unfortunately, replacing a shift solenoid or valve body is not an easy fix. You have to drop the gear tray to complete the job, so give yourself plenty of time.
READ MORE: 7 Symptoms of a Bad Shift Solenoid (& Replacement Cost)
4. Torque converter failure
The torque converter often fails because the transmission has not been properly maintained. If you use unwanted transmission fluid, don’t make changes, leave the dirty filter installed, and ignore signs that it needs attention, you may end up with a bad torque converter.
When the converter starts to fail, you may notice some signs before the car stops rolling. Initially it may make strange noises, especially when starting up. The sounds may disappear as the car warms up. However, it will begin to stagnate as the condition worsens.
The torque converter is usually an expensive part. Additionally, the repair can take all day because the transmission must be removed. This could be another task for a transmission specialist.
5. Worn clutches
The automatic transmission contains clutches, similar to the manual transmission. When the clutches wear out, the automatic car does not move. Clutch plates are responsible for connecting the transmission to the engine, so they can cause a lot of problems when they fail. Before the car stops, there may be a hiss or squeak when changing gears. You may also notice that the change becomes more abrupt.
Changing worn clutch discs is not an easy solution. As with many automatic transmission failures, you must remove the transmission and many components to complete the job. If you don’t know how to do it, it’s best to seek help.
6. Defective gear position sensor or shift lever
If the gear position sensor or switch sends an incorrect signal to the transmission control unit, it can cause problems. For example, if the gear is in D or first, but the TCM thinks it is in neutral, your car will not move. However, this is often quite easy to recognize, just look at the dashboard of your car and see if the gearbox matches the shift position.
RELATED: 8 Symptoms of a Bad Automatic Transmission (& Replacement Cost)
7. Faulty transmission control unit
In some cases, the faulty transmission control unit is easy to diagnose as it can display the wrong gear on the dashboard. When the transmission control unit is not working properly, the car does not seem to shift, even when the RPM increases. It may also go nowhere.
However, a faulty battery can also prevent this system from working properly because it does not have the proper amount of power. To start, check your car’s battery to make sure it is properly charged.
If that is not the problem, you may need a new transmission control unit. These parts can be difficult to access, requiring a qualified technician to work on them. If you’re not sure, have a professional take a look.
Also, make sure the handbrake is not engaged as this could be a stupid but easy mistake to make!
How to diagnose automatic transmission problems
If you want to fix the problem on your own, here are some tips you can follow.
- Start by checking the transmission fluid. If it’s low, fill it up.
- If the fluid is low, you should check for a leak. Leave a piece of cardboard under the car overnight to see where the leak is coming from.
- If you haven’t replaced the filter, it’s time to change the transmission fluid and filter. Check the filter to see if it is clogged.
- Check the shift lever and make sure it shows the correct gear on the dash as the shift lever position.
- Read the trouble codes on the transmission control module with an OBD2 scanner and look for any codes related to the valve body or shifter solenoid. Follow the instructions and repair any transmission-related codes.
- If nothing else works, check the battery voltage. If the battery is not charged, it may cause problems with the control unit.
If after these steps, you cannot discover the problem, it may be time to take the vehicle to a qualified workshop. Mechanics with specialized transmission diagnostic equipment can identify problems faster and have the skills to fix them. If your vehicle requires a transmission rebuild, it is not a task you want to perform in your home garage unless you have a transmission jack and other specialized tools.
RELATED: Should You Repair, Rebuild, or Replace Your Car’s Transmission?
How does an automatic transmission work?
The automatic transmission system works differently than the manual gearbox, which requires you to change gears. The automatic uses sensors that indicate when the change should occur and perform the action for you. No intervention is required on your part to keep the car moving.
Inside the automatic transmission, hydraulic fluid is used to maintain gear shifting. Most automatic cars contain the following selections:
- Park (P): The gears are locked and the wheels do not spin.
- Reverse gear (R): Reverse gear is engaged, so you can go backward.
- Neutral (N): This freewheeling mode releases all gears, allowing the wheels to spin without power.
- Drive (D): The car can move forward, progressing through all available gears.
- Low (L): The car stays in the lowest gears, ideal for towing or climbing steep grades.
Some cars eliminate low gear for a manual (M) option. With this setup, you can manually shift your automatic transmission.
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