Table of Contents
Experiencing issues with your automatic car not shifting gears can be frustrating and even alarming, especially when unsure what’s causing the problem. Whether your car hesitates to change gears, gets stuck in a particular gear, or fails to shift altogether, understanding the potential reasons behind these issues can help you address them quickly and efficiently. In this article, we’ll explore the most common causes of an automatic car not shifting gears, providing you with the insights needed to diagnose the issue and take appropriate action.
1. Low Transmission Fluid
Transmission fluid is essential for the proper operation of an automatic transmission. It serves multiple functions, such as lubricating the moving parts within the transmission, providing hydraulic pressure, and cooling the transmission system. When the fluid level is low, the transmission cannot function correctly, leading to difficulty shifting gears, gear slippage, or even complete transmission failure.
How It Affects Shifting: Low transmission fluid results in insufficient hydraulic pressure, crucial for the transmission to engage and shift gears smoothly. Without enough fluid, the transmission may struggle to engage the appropriate gear, causing delays or failure to shift. Additionally, low fluid can lead to overheating, which can further damage the transmission components.
Prevention and Solution: Regularly checking and maintaining the correct transmission fluid level is essential to prevent issues with your automatic car not shifting gears. If your car isn’t shifting correctly, checking the transmission fluid level should be one of the first steps. If the fluid is low, topping it off may resolve the issue, but it’s also important to investigate why the fluid level was low in the first place—there could be a leak that needs to be repaired. McCullough NAPA Auto Care can perform a thorough inspection to identify any leaks and ensure your transmission fluid levels are optimal, preventing further complications.
2. Faulty Shift Solenoid
The shift solenoid is an electromechanical component within the transmission that controls the flow of transmission fluid, allowing the transmission to shift gears at the right time. The transmission control unit (TCU) sends signals to the solenoid, telling it when to open or close to regulate the fluid flow and initiate gear changes.
How It Affects Shifting: A faulty shift solenoid can disrupt the timing and sequence of gear shifts. If the solenoid is stuck open or closed, it may prevent the transmission from shifting into the correct gear, leading to erratic shifting, stuck in a particular gear, or complete failure to move. This issue is often accompanied by warning lights on the dashboard, such as the check engine light.
Prevention and Solution: Regular maintenance can help prevent solenoid failure, as contaminated or old transmission fluid can cause the solenoid to stick or fail. If you suspect a faulty shift solenoid, it’s important to address it promptly to avoid more significant transmission problems. McCullough NAPA Auto Care’s ASE-certified technicians can diagnose and replace a faulty shift solenoid, ensuring that your transmission shifts smoothly and reliably.
3. Low Transmission Fluid Pressure
Transmission fluid pressure is generated by the transmission pump, which is driven by the engine. This pressure is vital for the operation of the transmission, as it enables the transmission fluid to flow through the system, engaging the gears and allowing the car to shift correctly.
How It Affects Shifting: If the transmission fluid pressure is too low, it can lead to problems with gear engagement. The transmission might struggle to shift or may not shift at all. Several factors, including a worn-out pump, a clogged filter, or low fluid levels, can cause low fluid pressure.
Prevention and Solution: Maintaining proper fluid levels and regularly changing the transmission filter can help prevent issues with fluid pressure. If you experience low fluid pressure, it’s critical to identify and repair the underlying cause, which might involve replacing the transmission pump or addressing other internal transmission issues. McCullough NAPA Auto Care can comprehensively check your transmission system, ensuring that fluid pressure is maintained and your car continues to operate efficiently.
4. Bad Transmission Control Module (TCM)
The Transmission Control Module (TCM) is the brain of an automatic car’s transmission system. It monitors various inputs, such as vehicle speed, engine load, and throttle position, to determine when and how to shift gears. The TCM sends signals to the shift solenoids to control the gear-shifting process.
How It Affects Shifting: A malfunctioning TCM can lead to incorrect or delayed gear shifts, or the transmission might not shift at all. Symptoms of a bad TCM include erratic shifting, being stuck in a particular gear, or the car going into “limp mode,” where it’s stuck in a single gear to prevent further damage.
Prevention and Solution: While the TCM is generally reliable, electrical issues, corrosion, or damage to the wiring can cause it to fail. Diagnosing a bad TCM often requires specialized tools to read error codes and assess the system. If the TCM is faulty, it must be repaired or replaced. The experienced team at McCullough NAPA Auto Care can diagnose TCM issues and provide the necessary repairs or replacements to restore your car’s optimal performance.
5. Broken Shift Cable
In vehicles with automatic transmissions, the shift cable connects the gear shifter inside the car to the transmission. When you move the shifter, the cable transmits this movement to the transmission, allowing you to select the appropriate gear.
How It Affects Shifting: A broken or stretched shift cable can prevent the transmission from engaging the correct gear. You might move the shifter, but if the cable is damaged, the transmission may not respond, leaving the car in the wrong gear or unable to shift altogether. Sometimes, the vehicle may be stuck in “Park” or “Neutral.”
Prevention and Solution: There isn’t much you can do to prevent a shift cable from breaking other than avoiding excessive force when shifting gears. If the shift cable is broken, it will need to be replaced. McCullough NAPA Auto Care can replace your shift cable, ensuring your car responds correctly when shifting gears.
6. Shift Lock Engaged
The shift lock mechanism is a safety feature that prevents the car from being shifted out of “Park” unless the brake pedal is pressed. This feature is designed to prevent accidental gear changes that could cause the car to move unexpectedly.
How It Affects Shifting: If the shift lock mechanism is engaged, you won’t be able to shift out of “Park.” This is often due to a failure in the shift lock solenoid, a blown fuse, or a problem with the brake light switch. Sometimes, it can be a simple issue of the car being on an incline, which can put pressure on the transmission and make it difficult to shift.
Prevention and Solution: To avoid problems with the shift lock, always press the brake pedal fully before attempting to shift out of “Park.” If the shift lock is engaged and you can’t shift, try pressing harder on the brake pedal or using the manual shift lock release (usually a small slot near the shifter). If the problem persists, the shift lock solenoid or brake light switch may need to be checked and repaired. McCullough NAPA Auto Care can diagnose and resolve shift lock issues, ensuring your vehicle operates safely and efficiently.
7. Worn Out Bands
Inside an automatic transmission, bands connect and disconnect the gears, controlling which gear is engaged at any given time. These bands are made of steel and lined with friction material, and they tighten around parts of the gear assembly to hold specific gears.
How It Affects Shifting: Over time, these bands can wear out, lose their friction material, or even break. When this happens, the transmission may be unable to hold a gear properly, leading to slippage, difficulty in shifting, or the inability to shift into certain gears.
Prevention and Solution: Regular transmission service, including fluid changes, can help prolong the life of the bands by keeping them lubricated and free from excessive wear. If the bands are worn out, the transmission must be disassembled to replace them, which is a complex and often expensive repair. McCullough NAPA Auto Care’s skilled technicians can service your transmission regularly to prevent band wear and perform the necessary repairs if your bands are already worn out.
8. Failed Throttle Position Sensor (TPS)
The Throttle Position Sensor (TPS) monitors the throttle’s position in relation to the accelerator pedal and sends this information to the engine control unit (ECU) and transmission control module (TCM). Based on engine load and speed, this information determines the correct timing for gear shifts.
How It Affects Shifting: If the TPS malfunctions, it may send incorrect signals to the TCM, causing improper or delayed shifting. Symptoms of a failed TPS include erratic shifting, hesitation during acceleration, or the transmission being stuck in a particular gear.
Prevention and Solution: A faulty TPS is often caused by wear and tear or contamination. Regular maintenance of the engine and its components can help prevent TPS issues. If the TPS fails, it will need to be replaced, and the new sensor must be calibrated to the vehicle’s ECU. McCullough NAPA Auto Care can diagnose, replace, and calibrate your TPS, ensuring that your transmission shifts correctly based on accurate throttle input.
Schedule an Inspection with McCullough NAPA Auto Care
If your automatic car is not shifting gears, it’s essential to address the issue before it leads to more severe and costly repairs. At McCullough NAPA Auto Care, we can diagnose and repair your transmission issues to keep your car running smoothly. Don’t let transmission problems linger—schedule your complimentary appointment with us today.
FAQ Why Your Automatic Car Isn't Shifting Gears
Fixing an automatic transmission that isn’t shifting involves diagnosing the root cause. Common fixes include topping off or replacing low transmission fluid, replacing a faulty shift solenoid, repairing or replacing a damaged transmission control module (TCM), and addressing any mechanical issues such as a broken shift cable or worn-out transmission bands. For a precise diagnosis and repair, it’s best to consult professionals like the ASE-certified technicians at McCullough NAPA Auto Care.
An automatic transmission may not go into gear due to various issues, including low transmission fluid, a faulty shift solenoid, a malfunctioning transmission control module, or mechanical problems such as a broken shift cable or worn-out transmission bands. Electrical issues, such as a failing throttle position sensor (TPS), can also prevent the transmission from shifting into gear.
W
hen your car won’t shift gears, the first step is to check the transmission fluid level. If the fluid is low, topping it off may resolve the issue. If the fluid level is adequate, the problem could be more complex, such as a faulty shift solenoid, damaged shift cable, or malfunctioning transmission control module. In such cases, it’s advisable to bring your car to a trusted repair shop like McCullough NAPA Auto Care for a thorough inspection and professional repair.
S
igns of a failing automatic transmission include difficulty or delays in shifting gears, strange noises such as whining or grinding, the car slipping out of gear, or the vehicle going into “limp mode” where it stays in a single gear. Additionally, warning lights like the check engine light may illuminate. If you experience any of these symptoms, it’s important to have your transmission inspected by professionals to prevent further damage.
Several factors can stop an automatic transmission from shifting, including low transmission fluid, a malfunctioning shift solenoid, a bad transmission control module, a broken shift cable, or mechanical wear and tear such as worn-out bands. Electrical issues, such as a faulty throttle position sensor (TPS), can also interfere with the transmission’s ability to shift gears properly.
Yes, low transmission fluid can cause the transmission to stop shifting. Transmission fluid is essential for providing the hydraulic pressure needed to engage gears. Without enough fluid, the transmission may not have sufficient pressure to shift, leading to delays or a complete failure to shift gears. If you suspect low transmission fluid, it’s important to check the level and top it off, or better yet, have it inspected by professionals.
No, tire rotation and alignment are separate services. Tire rotation involves moving the tires to different positions, while alignment adjusts the angles of the wheels to ensure they are set to the manufacturer’s specifications.
