Automatic Transmission Not Shifting Into 4th Gear [5 Easy Solutions] 

Automatic transmission not shifting into 4th gear! It is because of low transmission fluid levels, defective solenoids, and sensor problems. Therefore, a faulty OD switch and fault at the transmission itself also cause the transmission to not shift gear into overdrive (4th).  

Fortunately, we will describe every reason behind those faults and suggest certain ways to fix those issues. So, continue to read to explore the solution that will make the gear shifting a lot smoother. 

Automatic Transmission Not Shifting Into 4th Gear [5 Easy Solutions]

Why won’t my automatic transmission go into gear? This chapter will reveal the why and the potential solution to each problem. 

1. Low Transmission Fluid Level

A low level of transmission fluid will cause a low level of pressure. But there should be sufficient fluid pressure to shift the gears smoothly. Due to the low fluid level, you will get slower engagement when shifting gears. 

Solution:

It’s a basic inspection and you can do it yourself. Just start with checking the transmission fluid level. If needed, refill the transmission with fresh fluid. Also, make sure there is no dirty fluid in the transmission. 

2. Defective Solenoids

A faulty transmission solenoid is the main culprit that causes your transmission to not shift from one gear to the next. 

In an automatic transmission, the transmission uses the solenoid to shift gears. The solenoids generally control or regulate the flow and pressure of the fluid. They should supply the right amount of fluid through the system to make a proper gear shifting in automatic vehicles. 

Basically, the transmission control unit sends signals to the solenoids, which causes the solenoid to open to let the trans fluid flow into the valve body. As a result, your transmission can shift the gear to the next. 

If the solenoid gets bad, it will prevent your car from shifting up from a lower gear to higher like the 4th gear. You will hear it when driving as the RPM will keep climbing. And you will fail to accelerate anymore. In short, you will be stuck in 1st or 2nd but fail to shift into 4th gear. 

Now, you may ask- how can I understand that the solenoid is at fault? Well, the following signs will let you know about a bad solenoid: 

• Unusual gear shifting
• Delayed or slow gear shifting
• Fail to downshift 

Solution:

First off, we need to find out the source of the issue that causes the transmission solenoid to fail. It may be either the wiring, shift solenoid, transmission control unit, or other mechanical problems. 

Before getting into the troubleshooting steps, it’s worth researching and reading the error codes to understand the problem. 

Flushing and replacing the transmission fluid can solve most shift solenoid-related problems. 

We recommend you get a scanner tool to detect the solenoid problem error-freely. Once you get the scanner, check the wiring diagram of the transmission. Next, locate the pin that goes to the affected solenoid. Remove the transmission wiring plug and use the scanner tool to read the trouble codes. If you get the P0744 or related like this, we bet it’s the problem with the solenoid. 

Regarding this, you should replace the transmission solenoids. It may cost you around $50-$150 to change the solenoid. Sometimes, you may need to replace the entire solenoid pace, which will cost you around $300 to $400. 

3. Sensor Issue

The automatic transmission system has several sensors. The TCM will receive information from those sensors and allow you to shift the gear to the next smoothly. For example, every automatic transmission has a sensor in the transmission pan that senses the fluid temp. 

If it gets bad, you fail to shift the gear into overdrive (4th) as the sensor fails to sense the fluid temperature. And guess what, it’s impossible to shift the gear into overdrive until the trans fluid reaches a certain temperature. 

Similarly, a bad DSS (differential speed sensor) or a faulty VSS (vehicle speed sensor) also cause the transmission to not shift the gear. 

Solution:

A scanner tool is a must to find out the sources that cause the sensors to fail. We recommend you bring your car to a certified car mechanic. He will help you diagnose the sensor issues and solve them for you.  

4. Faulty OD Switch

An OD switch allows you to cruise at a modest or balanced speed while keeping the RPM reduced. This overdrive switch helps you engage or disengage overdrive or shift the gear into 4th. If this switch is at fault, the transmission fails to shift into 4th gear or overdrive. 

Solution:

We recommend you check the OD switch and its wiring. Make sure the wiring from the overdrive switch to the computer doesn’t get loosened. If the wire comes loose, tighten it up. On the other hand, if the wiring is okay, we bet the OD switch gets defective. Replacing it with a new one will be an easy fix. 

5. Defective Automatic Transmission

If everything is okay like the transmission solenoid, sensor, and OD button, we suspect the automatic transmission is at fault. To avoid this issue, you should repair or replace the transmission to shift the gear smoothly. 

Solution:

Replacing an automatic transmission requires a lot of skills. So, we recommend you bring your car to a certified mechanic. They will help you repair the transmission. If needed, they can also replace the transmission, which will leave a dent in your wallet. 

FAQs:

Conclusion

Automatic transmission won’t shift into 4th gear due to low fluid level, defective transmission solenoids, or a faulty OD button. What you need to do to shift the gear into overdrive (4th), you should address and troubleshoot those problems. Fortunately, we broke down everything above.

So, follow the troubleshooting steps we mentioned to solve the gear shifting issue. Otherwise, we recommend you go to a professional mechanic if those steps fail to fix your problems.