Automatic Transmission Not Shifting Into High Gear: Reasons and Fixes

If your car’s automatic transmission not shifting into high gear, it is most likely that there is a lack of fluid in the system. This occurs when an oil seal has worn out, allowing leakage of automatic transmission fluid (ATF).

Automatic Transmission Not Shifting Into High Gear

If this problem persists, it is important to identify the underlying cause and address the issue immediately. In this article, you will gain helpful insights into the main causes of this specific type of auto transmission (AT) problem and the right solutions.

What Is Causing Your Automatic Transmission Not Shifting Into High Gear?

Your car’s automatic transmission not shifting into high gear can be caused by an internal problem affecting the system’s performance. The common causes can include a lack of transmission fluid, throttle cables coming loose, problems with the shifter cable, and damage to the friction clutch.

– Lack of Transmission Fluid

The first step is to check the transmission fluid level. This fluid is required in the right amount to create the pressure required to move the different components inside the AT system. When this fluid level is low, the transmission won’t shift when accelerating. It is important to keep the following relevant points in mind:

  • Leakage is the most common cause of low fluid levels.
  • Worn-out or damaged oil seals, damaged pipe connections, and a faulty membrane within the vacuum corrector can cause oil leaks.
  • When there is a transmission fluid leak, the moving parts within the system can no longer work properly, thus creating gear-shifting issues.

Both automatic and manual transmission systems are sealed units. So, when you notice fluid outside the system, it usually means there is a problem. When a burning smell accompanies leaks, it is of more serious concern. 

Leaks from the AT system are unique and can be identified more easily. It will usually have a sweet burnt odor. The problem may also be accompanied by the issue of the gears getting overheated from excessive friction.

– Throttle Cables Coming Loose

The function of throttle cables is to control the accelerator pedal’s position. When they come loose, this can affect the functioning of the AT system. Here are some important points you should know about these cables:

  • When these thin metal wires lose tension, or there is a connection failure, the AT system no longer responds the way it should when pressure is applied to the pedal.
  • When there is a fault in the accelerator cables, you will come across the problem of AT not shifting into a higher gear. Besides, the gears will no longer shift as smoothly. 
  • If the cables break, the transmission system will stop working.

– Shifter Cable Problems

Automatic transmission cars usually have a cable that connects the shifter to the transmission system. The cable is designed in such a way that the indicator needle is properly aligned with the desired gear. When this cable gets damaged or becomes faulty, the needle will not align. This can result in problems with shifting gears. The shift linkage usually gets damaged or dislodged due to rough bumps or accidents.

Shifter Cable Problems

When there is a linkage failure, there will be problems with the way the transmission works. If the problem is not fixed in time, the issue can progress and deteriorate. The cable can stretch over time, or the linkage collet can come loose. This can change the length of travel the cable has to make between different positions. This change in length of travel may no longer be enough for changing gears.

– Damage to the Friction Clutch

Sometimes, the clutches inside the system can wear away or get damaged. This can also create shifting problems. Antifreeze may enter the system and cause damage to a clutch. When ATF and coolant mix together, it can cause faster clutch wear.

– Fault With the Sensors

There are multiple sensors for accurately monitoring the transmission speed so that the correct gear and gear ratios are selected. The main functions of the different sensors are as follows:

  • Transmission Speed Sensors: These sensors send signals to the powertrain control module (PCM).
  • Input Sensor: This sensor monitors the input speed of the transmission.
  • Output Sensor: This sensor monitors the output speed.

When any of these sensors develop faults, the PCM is unable to match the current gear with the next one. When this happens, the check engine light will be turned on, and the system will not shift into higher gears.

– Faulty Shift Solenoid

The function of shift solenoids is to control the flow of fluid. They open or close based on the electrical signals received from the engine. Speed sensors present in the engine provide the relevant data for this system to operate. 

Solenoids can also wear out like other components in your car. A problem with these parts can also prevent your car from shifting. Some of the signs of a faulty solenoid include:

  • Delay in gear shifts
  • Gear shifting becoming slow and hard
  • Unable to shift gears, and the engine keeps revving even when brakes are applied

– Shift Lock Problem

The auto gearbox is designed not to shift out of the ‘park’ mode unless the system detects a person in the driver’s seat and a foot on the brake pedal. This system is an important safety feature that prevents your car from rolling when a passenger or kid bumps the shifter. 

Reasons for Automatic Transmission Not Shifting

It can malfunction and prevent the AT from shifting into gear. However, there is a shift lock release option in your car that can help overcome this problem, and you can find its location in your owner’s manual. 

– Faulty Charging System

A faulty charging system can also cause the automatic transmission not shifting into high gear. It can cause a dead or weak battery and prevent the solenoid from engaging or the shift lock from disengaging. If this happens, the check engine light can get turned on, thus preventing the ECM from running the solenoids. This can further prevent the gears from shifting.

– Problematic Torque Converter

There are many components inside the converter that can go bad, thus preventing the gear from shifting. This includes parts such as:

  • Pump
  • Turbine
  • Stator

When such components become faulty, you can face slipping issues when the system shifts gears. These internal parts can block the transmission and prevent shifting.

– Contamination in Transmission Fluid

It is not just the level of the fluid but also its condition that can create problems with the gears shifting. Dirt and debris can build up in the transmission fluid when it starts getting old. When the fluid becomes degraded, it becomes increasingly difficult for the system to change gears. Timely fluid flushing and replacement are important for preventing permanent damage to the AT system.

– Faulty Vacuum Corrector

The vacuum corrector contains a membrane that reacts based on the level of the vacuum. When the membrane becomes faulty, the fluid inside the transmission can enter the car’s engine. While the system can continue working for a long time with the reduced level of lubrication, it is eventually going to fail.

Sometimes, the pipe that goes between the AT system and the oil cooler can get damaged. This can cause the fluid to leak, thus causing the problem of the gearbox not shifting.

– Extremely Cold Conditions

It is also likely that extremely low temperatures can cause the transmission system not to shift into higher gears. The low temperature can cause the fluid to thicken, thus preventing it from flowing effectively. The use of quality synthetic fluid can help prevent this issue from occurring.

– Damaged or Misaligned Gear Sets

When gear sets are damaged or misaligned, they will not engage as smoothly as they should. Your car will no longer be able to get into gear, and gears can grind against each other due to several reasons, including:

  • Worn-out gears
  • Failed/failing bearings
  • O-ring or internal seal leaks

This can result in the creation of metal dust and chips that damage other transmission parts.

– Faulty Adaptive Transmission System

Some vehicles have adaptive AT systems. They shift gears based on the driving patterns and the fluid’s condition. The system is designed to automatically shift gears when an abnormality in these conditions is noticed. This can make it difficult for your car to change gears.

You can experience the auto transmission problem in many different ways. The car may shift automatically and smoothly between two gears, but it wouldn’t shift into third gear or keeps getting stuck in first and second gears. Sometimes, the system stays in the second gear and doesn’t shift into a higher gear.

Other times, when you set the shifter into drive position, ‘D,’ and press the accelerator pedal, the car may not move. When you switch from automatic to manual transmission mode and the gears work normally, it again means you have a problem with the transmission. If your AT system works only in reverse gear, it can mean that the friction clutches, clutch rings, or piston collar need replacement.

You have an AT problem even when your transmission is slipping when your car starts moving. Suppose the transmission doesn’t engage in any gear. In that case, it may be due to a failing torque converter, lack of lubrication, damaged or faulty oil pump pinion, worn-out clutches, clogged filters, jammed valves, or broken collars. Your vehicle’s electronic control unit (ECU) can place the AT system in ‘safety’ mode when you have transmission shifting issues. 

So, these are some of the more common reasons why your automatic car won’t shift into higher gears.

How To Fix the Problem of Automatic Transmission Not Shifting Into High Gear?

You can fix the transmission won’t shift into a higher gear by using an OBD scanner to access the diagnostic error codes from your vehicle’s PCM or checking the underlying causes. When the cause of the problem has been diagnosed, a mechanic can help carry out the essential repairs.

Top-up the Transmission Fluid

On the other hand, if you can identify the underlying cause yourself, the following solutions can help get your AT shifting smoothly.

– Top-up the Transmission Fluid

If there is not enough ATF, the system will have a problem shifting correctly through the gears. Before you add more fluid, it is important to find the source of the leak. 

The common causes include worn out:

  • Oil seals
  • Gaskets
  • O-rings

Make sure to replace the faulty parts before you top up the fluid level.

It is recommended to ensure the fluid level is always maintained to prevent future AT system issues. It is also important to use a quality product when topping up the fluid.

– Replace a Damaged or Worn-out clutch

When a worn-out or damaged clutch causes AT problems, there is no room for repairs. When you have a corroded, worn-out, or damaged clutch that affects the transmission’s performance, the only solution is replacement with a new one.

– Tighten Throttle Wires or Other Loose Connections

If loose connections are what are causing your AT shifting problems, all you may have to do is tighten them up. There may be loose connections on the throttle wires or other areas in the AT system.

– Replace Faulty Sensors

Once you have ensured a low AT fluid level does not cause the shifting problem, you should next check the PCM. The PCM controls the transmission system’s functioning. If the speed sensor is faulty, the PCM will not get any input. A good way to ascertain this is to check whether the speedometer it is working properly.

Solutions for Automatic Transmission Not Shifting

As mentioned above, there are multiple transmission speed sensors at play. Any one of them failing can cause the AT system to stop shifting. When you have identified the sensor causing the problem, you will be required to replace them. 

– Use the Shift Lock Release

If the transmission doesn’t shift out of drive even when your foot is on the brake pedal, the problem may be fixed by releasing the shift lock. As mentioned above, the location of your car’s shift lock release can be found in the owner’s manual. The ‘lock release’ is in the form of a tiny slot and can usually be found near the steering column or clutch.

– Check the Error Codes for Automatic Transmission Not Shifting Into High Gear

Whenever your car’s computers encounter a fault, an error code is set. These codes can be read with the help of an OBD scanner, allowing you to learn about the underlying issue. Different vehicles have different codes, but there are universal codes as well. When you notice any error codes, a little online research can help you identify the proble

Next, you should ensure the valves are working correctly. You will have to replace them if they are jamming. Usually, internal transmission repairs should be left for well-trained mechanics to handle professionally. The repair must involve thorough flushing of the gearbox case, radiator cooler, and valve body as part of the overall process.

Thus, many factors can cause a problem with your car’s auto transmission system. It is not just low fluid levels but also the use of incorrect fluid specifications that can create trouble. The way you drive your car can also create AT system problems or deteriorate an existing problem.

FAQs

1. How To Fix Automatic Transmission Not Shifting Into Third Gear?

Changing the transmission fluid helps fix a lot of transmission issues, but if the problem persists, you should check the accelerator cables. Sometimes, this issue is created by a defective cable having excess slack.

2. What if the Automatic Transmission Is Not Shifting at All?

AT shifting issues are often caused due to faulty seals and oil leaks in the system. If your car’s transmission is not shifting at all, it is best to get the help of a car mechanic to diagnose the problem.

3. How Much Can It Cost To Replace an Automatic Transmission Solenoid?

The cost of replacing a transmission solenoid depends on your vehicle, location, and mechanic. On average, the job should cost anything from $200 to $500.

4. What Are the Signs That a Transmission Filter Is Clogged?

Automatic transmission problems can occur when the ATF gets dirty, and the transmission filter gets logged. This prevents the internal components from getting the lubrication required for proper functioning. The signs include the AT not shifting effectively or slipping, the engine running rough, or a lack of power.

5. What Are the Signs of a Faulty Solenoid?

Some of the common signs of a bad solenoid include delayed shifting, unable to shift out of neutral, and shifting becoming slower and harder.

6. How To Prevent Your Automatic Transmission System From Failing?

If you want to prevent AT from not shifting in the future, it is recommended to check the ATF regularly. You should also switch gears properly and use the parking brake. Further, allow your car to warm up before going out and avoid overloading.

Conclusion

The information mentioned above should help you figure out what may be causing your car’s AT system to not shift. 

  • It may be caused by low fluid levels, loose accelerator cables, faulty sensors, clutches, or torque converter. 
  • Even contamination in the fluid can cause such a shifting problem. 
  • Once you have identified the right cause, it should become easier to address the problem.

The information mentioned above should also help you prevent the problem of automatic transmission not shifting into high gear from reoccurring in the future.

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