Why Is My Automatic Car Not Changing Gear?

There is more than one answer to the question, ‘why is my automatic car not changing gear?’ With different causes comes different solutions. If you are wondering why your automatic car is not changing gear, you’ve come to the right place.

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Most modern cars are equipped with an automatic transmission. It is designed to optimize the efficiency of the engine and at the same make driving as easy as possible. You might ask what happens if the automatic transmission fails to do its main job of changing gears. 

The automatic transmission has plenty of complex components inside it, and failure of any of those parts can lead to drivability issues, if not complete loss of driving capability. In this article we will try our best to answer the question, ‘why is my automatic car not changing gear?’

Possible Causes: Why is my automatic car not changing gear?

Here are three possible causes that may answer the question ‘Why is my automatic car not changing gear’:

• Shift Interlock Mechanism 

Modern automatic transmissions come with a shift lock feature which prevents you from inadvertently shifting out of drive while the car is moving, or out of park while the engine is off. 

You can only shift your automatic transmission when the engine is on and your foot is on the brake. If you’ve met these conditions and the transmission still won’t change gear, try the shift lock release. 

Refer to your car owner’s manual to help you find the shift lock release on your car. It might be a small slot that you can slide the key into on the steering column or console. Doing this will reset the shift interlock mechanism and must allow you to shift the transmission again. If not, chances are you need to replace your brake pedal position sensor with a new one or other transmission repair might be needed. 

• Failing Electronics

You might have an electronics issue if there is nothing mechanically that prevents your automatic transmission from changing gears. Inside an automatic transmission, there are electronic components known as solenoids. 

They respond to signals from the transmission control module which directs automatic transmission fluid pressure through opening and closing valves. This makes it possible for the transmission to change gear. When there’s a failed solenoid or a malfunctioning transmission control module, you may have difficulty in shifting gears or you may not be able to change gear at all. 

• Low or Dirty Transmission Fluid

Transmission fluid transfers engine power in an automatic transmission. Old transmission fluid can gather debris, stop functioning properly, lose viscosity, and need a periodic replacement. Also, when the transmission has a leak, and the fluid level becomes too low, you’ll have problems changing gears.

Solutions: Why is my automatic car not changing gear?

When the problem is with your automatic transmission, you want to have it fixed immediately at the lowest cost possible. Now that you already know the different causes of ‘why is my automatic car not changing gear,’ you can now check which among them is the culprit to your transmission issue.

Transmissions, in general, are too complex for an average Joe to fix. Without the right tools, you cannot fix advanced transmission problems yourself. However, what you can do is to diagnose the exact cause to make repairs easier for you and save money when you bring your car to the shop. 

The following steps are generally what you should do to find out the answer to your question, ‘why is my car not changing gear?’

1. Try to determine what’s causing the problem. Check under your car for any leaks. Try shifting your gears for any issues.

1. Check your transmission fluid. Most transmission issues are caused by either low levels of fluid or ineffectiveness of the fluid. You may need to completely change your fluid and filter if the fluid is contaminated, black, or burnt.

1. If the fluid is not the culprit, then check your car’s computer for any OBD (On-board Diagnostics) codes. If you want to check it on your own, you may buy an OBD scanner. It will often tell you what’s wrong with your transmission.

1. If the OBD scanner does not tell you anything wrong with the transmission, or if you cannot find a solution to the given code, the next thing to do is read the repair manual or website for your car’s specific make and model.

1. If none of the above steps help you figure out the cause of the problem, then it’s time to have your car check by a professional mechanic. 

Specific Solutions 

• Low Level Or Ineffective Transmission Fluid 

When checking the transmission fluid, make sure it is at the proper level as indicated in your owner’s manual. Having too much or too little fluid can cause mechanical failure. Most modern transmissions are manufactured as sealed units, but they should still be flushed to make it deliver optimum performance. 

If your transmission fluid is running low, you should add more fluid. But if your fluid is deep red or brown in color, murky, or is full of metal shavings, then it’s time to change it. 

• Computer System Problem

Other times you may be having a problem not changing gear because of a computer system issue. Sometimes all it takes is resetting your car’s computer system to solve the problem. To do this, disconnect the battery for around 30 minutes. This will reset your system. But if doing this doesn’t help then it’s time to let a professional mechanic do the job of diagnosing and fixing the problem.

Prevention: Why is my automatic car not changing gear?

Avoid the problem of your automatic car not changing gear and other automatic transmission problems altogether by following these tips for keeping your automatic transmission in good condition. 

• Check your transmission fluid as recommended in your car owner’s manual. In most vehicles such as cars, SUVs, and light trucks, checking the transmission fluid is as simple as checking the oil. 

When the engine is on idle, pull out the dipstick, wipe it off, insert again, wait, then pull it out to have an accurate reading. If the fluid is low, there might be a leak. The fluid should be a bright red in color, smell sweet and clear. If it’s dark red or brownish or smells rotten, then you should have a transmission repair technician inspect it. 

• Use the right transmission fluid. Refer to your car’s owner’s manual to know what type of transmission fluid you should be using. If you’re not sure, you can always check in with your trusted mechanic.

• Make sure your engine’s cooling system is in good condition by having it serviced periodically. Aside from preventing your engine from overheating, it also cools the transmission fluid pumping through the gearbox. 

• Flush your transmission regularly. You can change your transmission fluid on your own but it’s best left to a professional. Usually, you have to get your car’s transmission flushed once a year. How long your transmission fluid will last depends on how much driving you do and the car’s operating temperature. 

• Change your transmission filter regularly. Your car’s automatic transmission may come with a filter, and that needs to be changed from time to time. While most newer cars do not have a transmission filter, some still do depending on the make and model. 

• Avoid changing gears while your car is moving. Make sure to bring your car to a full stop before changing gears from drive to reverse or vice versa. 

• Allow your car to warm up before driving. Many drivers are guilty of hopping into their car, starting the engine, and driving right away. Let your engine warm up a few minutes before starting to drive, especially during cold months.

• Avoid driving on a spare tire for a long period of time. Having mismatched tires is a big no-no. It can damage other parts of the car like wheel alignment and also put unnecessary strain on your transmission.

• Do not use your car for towing as much as possible. Using it for towing heavy loads, especially in hot temperatures, can lead to oxidizing or burning the transmission fluid. This can cause a lot of damage to your car’s transmission.

• Schedule for a transmission inspection yearly. Have a certified transmission repair professional perform a diagnostic check for your transmission for leaks and other irregularities. Also, have your fluid level, color and smell check periodically.

Fixing your transmission can be expensive depending on how serious the problem is, the type of car you are driving and how old it is. Sometimes it is unavoidable to have a transmission problem but doing some preventative maintenance and practicing good driving habits can make your transmission last longer and reduces the chance of a total breakdown. 

When you are looking for the answer to the question why is my automatic car not changing gear, it is important to do so with urgency. When your automatic transmission is unable to change gear, it’s time to have a professional look at it. As mentioned earlier, transmission repairs can be costly. It’s best to have the issue address correctly and immediately to prevent more expensive and time-consuming repairs.