A vehicle transmission is a mystery to many motorists, and for a good reason. It is a complex mechanical part with many components fitted together.
It becomes more complex if you own a manual transmission because it’ll keep you busy throughout your journey.
However, once you master how to shift manual gears effectively, it becomes second nature. This means you’ll be changing the gears without paying much attention. You must resist this for smooth operations.
There are several reasons transmission will not engage in any gear, both in manual and automatic vehicles.
This article will discuss why transmission will not engage in any gears and the solutions to fix the problem. First, let’s start with the causes.
How Does the Transmission System Work?
To troubleshoot effectively, it helps to know the basics of how your transmission operates. Here’s a quick overview of automatic vs. manual transmission systems, and the key components like the torque converter and linkage, and how the shifter comes into play:
Overview of Automatic and Manual Transmissions
In a manual transmission, you have a clutch and a stick shift. You (the driver) are responsible for disengaging the engine (with the clutch pedal) and selecting the appropriate gear (with the shifter).
It’s a direct mechanical connection – when you move the shifter, you’re moving gears (via linkage) inside the transmission.
Manual gearboxes use gear oil for lubrication and typically don’t have pumps or hydraulics inside the transmission itself for shifting; it’s all driver input and mechanical synchronizers that match gear speeds.
In an automatic transmission, things are more complex internally but easier for the driver. There’s no clutch pedal. Instead, when you put the car in “Drive,” the transmission automatically changes gears for you as you accelerate or slow down.
It uses a combination of fluid pressure, a torque converter, and a set of planetary gears and internal clutches/bands to shift gears.
The car’s computer often controls when to shift by monitoring speed, throttle, etc. Automatic transmissions have fluid pumping through a valve body, which directs fluid to different circuits to engage gears.
Key Components: Torque Converter and Linkage
An example of a torque converter (disassembled). The torque converter in an automatic transmission takes the place of a clutch, using fluid to transfer power from the engine to the transmission.
Torque Converter
In an automatic, the torque converter is what allows your engine to keep running even when you’re stopped in Drive. It’s essentially a fluid coupling between the engine and transmission.
Think of it as the automatic’s version of a clutch. When you’re idling at a light, the torque converter lets the engine spin independently. When you press the gas, it uses fluid to “lock up” and transmit power to the transmission.
If the torque converter fails or its internal components (like the turbine or stator) are damaged, your car may not move in gear or might shudder and slip.
For instance, a broken torque converter can cause the vehicle to act like it’s in Neutral even when in Drive. Replacing a faulty torque converter is a common solution when an automatic transmission won’t shift or engage properly under load.
Shift Linkage (Gear Selector Linkage)
The shift linkage is the connection between your gear shifter (whether it’s the lever on the floor/column in an automatic or the stick in a manual) and the transmission’s internal gear selector. In many cars, this is a cable.
When you move the shifter to “D” or another gear, the cable moves an arm on the transmission, selecting that gear. If the linkage or cable is stretched, loose, or broken, the transmission might stay in Neutral or not fully reach the gear you intended.
For example, if the linkage cable to the transmission snaps, your car won’t go into gear at all because the command from the shifter never actually reaches the transmission.
Likewise, a misadjusted linkage might make the indicator say you’re in Drive while the transmission is actually between gears. The linkage is an often overlooked culprit for gear shifting problems – fortunately, it’s usually a relatively easy fix or adjustment.
How the Shifter Affects Gear Changes?
The way you operate the shifter can also impact gear engagement. In automatics, there’s usually a safety feature called a shift interlock: you have to press the brake pedal before you can shift out of Park.
If this interlock malfunctions (for instance, a bad brake switch), you might find the shifter physically won’t move out of Park.
In such cases, it’s not a transmission internal issue at all – it’s a simple switch or you may need to use the manual shift release button hidden near the shifter. Always ensure you’re pressing the brake when shifting an automatic out of Park.
For manuals, the equivalent is pressing the clutch before shifting. Forcing the shifter without the clutch can damage the gears.
Also, each gear has synchronizers to smoothly match speeds; if you grind gears, you’re wearing those out. Using the shifter properly (clutch fully depressed, not rushing the gear change) will keep things working well.
If you develop a habit of aggressive or improper shifting, you could end up with a transmission that’s difficult to get into gear over time.
Now that we understand the pieces involved, let’s move on to what you can do when faced with this issue. There are a few things you can check yourself before calling the mechanic.
What Causes Automatic Transmission Will Not Engage in Any Gear?
The automatic transmission will not engage in any gear caused by a lack of transmission fluid, bad brake switch, defective torque converter, bad shift interlock solenoid, and transmission slipping.
Some causes an automatic transmission will not engage in any gear:
- Bad Shift Interlock Solenoid
- Lack of Transmission Fluid
- Defective Transmission Control Unit
- Failing Torque Converter
- Transmission Slipping
- Bad Shifter Linkage
#1. Bad Shift Interlock Solenoid.
You probably know about shift interlock solenoid when you drive an automatic transmission or a modern car.
The shift interlock solenoid is a safety feature that comes with modern cars that keeps the driver away from accidentally shifting out of the park when the brake pedal is not pressed down.
For any reason, if the shift interlock solenoid cannot extend or retract, this safety mechanism doesn’t work as circumstances the car does not shift out of the park, so the car won’t go anywhere.
Hence, an automatic transmission will not engage in any gear for the bad shift interlock solenoid. Presently bad shift interlock solenoid is a common issue that is found in various vehicles, and fortunately, it’s easy to fix.
#2. Lack of Transmission Fluid.
Lack of transmission fluid is probably the most common reason to find when your automatic transmission will not engage in any gear.
Transmission fluid is a type of hydraulic fluid that keeps the car’s transmission gears and clutch away from hard shifts. When your car has the right and sufficient level of transmission fluid, the gear shifting will be smooth.
But, when low transmission fluid won’t be able to generate as much hydraulic pressure as transmission required, it leads to gear slippage.
Transmission fluid needs to change after running 80 thousand to 100 thousand miles. Both manual and automatic transmissions need to change the transmission fluid, but manual transmission fluid needs to change more frequently.
Be aware that engine oil is not the same as transmission fluid, therefore. So, check the level of transmission fluid when the car won’t go into gear.
#3. Defective Transmission Control Module.
When your automatic transmission is not engaging, you better be sure the car’s transmission control module is working properly.
The transmission control module (TCM), also known as the Transmission control unit (TCU), is responsible for the efficient function of the car’s transmission, just like the car’s engine control module (ECM).
A bad transmission control module provides wrong shifting signals that cause your car can experience incorrect or unintended gear shifting.
To keep the gear shifting smooth and efficient, the contribution of the transmission control module is necessary. That’s why ensure the transmission control unit is working as it should be.
#4. Failing Torque Converter.
The torque converter is a major component that engages and disengages the transmission from the engine in automatic transmission.
The automatic transmission torque converter consists of other components within that if any of the components goes bad, your car transmission will not engage in any gear.
Proper check-up of the torque converter can be technical; hence it’s better to leave this matter to a professional.
Note: Both manual transmission and automatic transmission get help from the torque converter to shift gears. So, test that torque converter and ensure it is working properly, whether your car is a manual or automatic transmission.
#5. Transmission Slipping.
Transmission slipping means when your car engine produces the power, but the power doesn’t get to the wheels.
When you notice the shifting is not smooth and the gear is not staying fully in the particular gear as you drive, then you are experiencing transmission slipping.
As is evident earlier, there are several causes of transmission slipping. The automatic and manual transmissions can slip, but transmission slipping is most common in automatic cars or trucks.
#6. Bad Shifter Linkage.
Shifter linkage is a strong and thick cable that connects the gear selector or gear shift to the transmission. Gear shift linkage and transmission shift linkage refers to the same thing in vehicles.
As you can understand, if the shift linkage is detached or broken, the gear selector will not connect to the transmission and this situation we describe as a car won’t go into gear commonly.
I commonly see an automatic transmission that won’t engage any gear because of the faulty shifter linkage. So, if the shifter linkage is broken, then replace or if it detached, then attract again.
What Causes Manual Transmission Will Not Engage in Any Gear?
The car’s manual transmission will not engage in any gear because of a worn or bad clutch, faulty transmission synchronizers, broken clutch pressure plate and shortage of clutch fluid.
Common causes a manual transmission won’t engage in any gear:
- Bad or Worn-out Clutch
- Shortage of Clutch Fluid
- Bad Clutch Master Cylinder
- Defective Clutch Pedal Assembly
- Bad Clutch Slave Cylinder or Clutch Fork
- Faulty Transmission Synchronizers
- Clutch Pressure Plate Failure
#1. Bad or Worn-out Clutch.
In any vehicle, the clutch is an important part of the transmission. Both manual and automatic transmission cars have a clutch that engages and disengages the car’s engine and transmission.
Because of the bad clutch, the manual transmission won’t go in gear. That is also the same scenario for the automatic transmission, but manual transmission cars suffer more.
The clutch disk can be worn out after long use. However, the clutch is a long-lasting component that supports transmission. So, when the clutch is bad, it simply cannot engage and disengage the transmission gear.
#2. Shortage of Clutch Fluid.
The clutch fluid sometimes refers to brake fluid because both have the same job in the vehicle. The clutch fluid is a type of oil or hydraulic fluid that is kept in the clutch master cylinder to facilitate gear shifting.
When the manual transmission does not engage in any gear, you should check the level of clutch fluid because the shortage of clutch fluid will definitely become an obstacle to smooth gear shifting.
In many cases, I found that for the leakage in the clutch master cylinder, a shortage of clutch fluid situation occurs. Typically, car owners should refill the clutch fluid every one and a half years to two years consecutively.
Fortunately, it’s easy to know the level of clutch fluid by looking at the clutch reservoir in a car’s engine bay.
#3. Bad Clutch Master Cylinder.
Manual transmission relay on the clutch master cylinder or clutch pump. The clutch master cylinder facilitates the mechanical movement of the clutch pedal to hydraulic pressure.
So, if your car has a failing clutch master cylinder, this will not be able to produce enough hydraulic pressure to engage or disengage the clutch.
Be aware of any leakages; the lack of brake fluid will keep your car’s clutch master cylinder safe and good.
#4. Defective Clutch Pedal Assembly.
Nowadays, car manufacturers are taking extra care to make the clutch pedal assembly long-lasting and operative. The clutch pedal assembly is also known as the brake pedal assembly.
A bad or defective clutch pedal assembly will not be able to operate the clutch and eventually make the transmission not engaging.
#5. Bad Clutch Slave Cylinder or Clutch Fork.
The driver of a manual transmission car will not be able to switch gears if the clutch slave cylinder is bad because a clutch slave cylinder is an integral part of the manual transmission.
With that being said, the clutch slave cylinder also needs a supporting part that is called a clutch fork. Hence, the manual transmission will not engage in any gear if the clutch slave cylinder and clutch fork are bad.
#6. Faulty Transmission Synchronizers.
The manual transmission synchronizer is responsible for the smooth engagement of gears. The synchronizer is only used in manual transmission.
Sometimes the manual transmission synchronizer also refers to the gear synchronizer. When the transmission synchronizer fails, the manual car’s gear won’t adjust shifting with speed, which damages the transmission and puts you in danger.
The easy way to determine a bad manual transmission synchronizer is to hear whirring or humming noises while you shift in a specific gear.
#7. Clutch Pressure Plate Failure.
A manual transmission will not engage in any gear if the clutch pressure plate is broken because the clutch pressure plate also assists the power to flow from the engine to the transmission.
The clutch pressure plate consists of a number of covers and releases fingers; therefore, if any of the fingers are broken, the clutch pressure plate will not be able to disengage properly.
An unconstrained or very loose clutch pedal feels like it is a sign of a bad or broken clutch pressure plate.
What To Do When Your Car Doesn’t Go Into Gear?
When the clutch is working properly, most gear-shifting problems go away. But, there are several solutions that you will need to consider if the car won’t go into gear.
Things you can do when the car doesn’t go into gear:
#1. Make Sure the Clutch is Working Optimally.
When you are driving a manual transmission car, and the car won’t go into gear, then it’s most probably because the clutch is not working as it should be.
A clutch might not work optimally because of pressure plate failure, broken clutch fork, wrong clutch pedal assembly, damaged throw-out bearing and more.
Mentioned any causes your car’s clutch can go bad instantly, and as you know, a faulty clutch is the most common reason why a manual transmission does not engage any gear.
So, if the car or truck won’t go into gear, check the clutch first, and make sure the clutch operates perfectly with gear shifting.
#2. Fill Up Transmission Fluid.
Topping off the transmission fluid can be a simple and easy solution when your car won’t go into gear because low transmission fluid prevents lubricating the transmission, so gear shifting becomes hard.
Now, the transmission fluid can be dirty, goopy or even burned, but a car needs fresh fluid in the transmission valve body.
So, along with checking the level, you also need to ensure the transmission is not dirty if it then replaces the transmission fluid with new.
#3. Press the Clutch Pedal Down More.
If you are looking for an instant solution for the car that won’t go into gear then, pressing the clutch pedal down a little bit more before changing gears.
When the clutch pedal is all the way to the floor, you need to try changing the gears again. This is also a common practice that most auto mechanics test when the manual transmission does not engage in any gear.
#4. Check Shifter Linkage.
As I described in the previous section of the article, what does the shifter linkage do. Therefore, checking the shifter linkage to ensure the cable is connected properly and not broken is another way to fix the car’s transmission engaging problems.
Since not every car owner doesn’t have enough knowledge about the car’s transmission, that’s why I recommend you check the shifter linkage with a mechanic.
#5. Replace the Faulty Transmission Control Unit (TCU).
Automatic cars use the transmission control unit (TCU) electric device to run efficiently, and the TCU is also connected to the car computer, known as ECM. But, a manual transmission car does not have a TCU.
Worn-out wiring or wrong cable connection between the transmission control module (TCM) and the car’s other electric devices can make the transmission control unit bad.
#6. Try To Put Your Car Into a Different Gear.
Another quick and useful thing to do when the transmission is not engaging is to try to put the car into a different gear fast.
You can easily determine which gear is not shifting by trying to put your car into a different gear.
How much does it cost to fix engaging Transmission Problems?
The average cost of fixing transmission engaging problems ranges from $100 to $1000. If the culprit is a low or dirty transmission fluid, then you should budget to spend around $100 to $300 by buying a new fluid, flushing, and refilling the transmission.
If a faulty clutch is a cause in your manual transmission, it’ll cost around $400 to $1000 to replace the faulty components.
FAQs.
Q: Why won’t my car move when I put it in drive or reverse?
Several factors can cause a vehicle not to move in drive or reverse. The primary cause of this malfunction is worn-out clutch components that don’t have enough materials to withstand the weight and friction of the vehicle.
Other probable causes of this malfunction are faulty shift lock, broken or dislodged transmission, low transmission fluid, bad torque converter, and lousy TCM.
Q: What does it mean when a car won’t go into gear?
Whether you have a defective manual gearbox or automatic transmission, your car may fail to go into gear at any time. This means you’ll be stranded wherever this happens until you track and fix the culprit.
Q: What causes a transmission to go in reverse but not forward?
There are three main reasons a transmission may only move in reverse and not forward. These include low transmission fluid, faulty speed sensors, and defective transmission components.
Low transmission fluid: If your transmission fluid is too low, it will prevent the tranny from shifting properly. It can also cause it to only move in reverse and not forward.
Faulty speed sensor: Take it or leave it; a faulty speed sensor can cause a transmission to move only in reverse gear. The speed sensor features a magnetic sensor that enables smooth gear shifting inside the transmission unit.
It tells the car computer how fast the vehicle is traveling. If it fails, it will send a false signal to the car computer and prevent it from moving forward or reverse.
Faulty transmission components: There are several transmission components involved. A faulty transmission solenoid, a lousy computer that controls the car, or other defective internal components can prevent a vehicle from moving forward.
Q: What causes an automatic car not to move in drive?
As explained earlier, automatic transmissions function in hydraulic dynamics. They rely on the transmission fluid to work properly.
If they run low on fluid, it’ll affect the smooth running. Whenever you shift into any gear, the car computer activates the transmission solenoid to allow fluid to flow into the valve body.
The transmission control unit, on its own, receives and processes the data from all tranny components. The speed sensor signals the TCM or PCM how fast the vehicle travels.
Therefore, a low transmission fluid, defective transmission solenoid, lousy speed sensor, faulty valve body, or bad TCM can prevent a vehicle from moving in the drive.
Q: Can a fuse cause transmission problems?
Of course, a blown a fuse can cause transmission problems. A fuse connects the transmission solenoid and the TCU. So, if any malfunctions or issues occur on these fuses, sensors, or associates, it’ll cause transmission problems.
Final words
There are many reasons transmission will not engage in any gear. We have outlined the causes above and how to fix the problem. The most common amongst them is low transmission fluid.
When wondering, ‘why won’t my gear shift engage?’ Check the tranny fluid level and refill it to the recommended level if it’s below the gauge. A common top-up can fix the problem.
If the low fluid is not the problem, you can check the probable causes above. It’s recommended to fix issues on time before it escalates into major problems.