Can A Bad Alternator Cause Transmission Problems [Solved]

There are no isolated systems in modern cars as all systems are somewhat interconnected. If you have a bad alternator and transmission issues at the same time, you may suspect that one is affecting the other. So, can a bad alternator cause transmission problems?

can a bad alternator cause transmission problems

Even though it may sound crazy to you at first, the short answer is that yes, a bad alternator can lead to transmission problems. Keep reading this article to find out all about it in detail.

We’ll also discuss how you can recognize transmission issues in your car and what are the other reasons behind it besides a bad alternator. So, let’s dive in!

Can A Bad Alternator Cause Transmission Problems [Solved]

The transmission system in your car is responsible for transferring your engine’s power to the wheels in your car using a series of gear or ratio changes.

There are many different types of transmissions out there including automatic, manual, continuously variable (CVT), dual-clutch (DCT), and more.

It may seem like the alternator and the transmission system are not connected to each other on the face of it. But let’s look deeper into this and understand how they are related to each other.

The alternator charges the battery in your car and also powers the electrical components when you’re on the move. There are three common scenarios in which a bad alternator can lead to transmission issues.

1. Voltage Drops

The alternator needs to generate a certain number of minimum volts to make sure that it powers all the electrical components. When you have a bad alternator that fails to do so, the ECU in your car has an important decision to make. It chooses which components to cut off.

voltage drops

The ECU can cause programming changes to ensure that the engine RPM stays at a low level to minimize the load on the engine. Similarly, some transmissions can also be programmed to keep the engine locked at a lower gear to enhance the alternator speed and the RPM.

When a bad alternator leads to transmission issues, this voltage drop will be the main reason behind it most of the time. It’s a simple mechanism of the ECU to distribute the limited power generated by a bad alternator.

It can often put your car into limp mode as well. Check out our guide on how a bad alternator can cause limp code and false codes in your car.

2. Voltage Surges

The previous issue was a programming mechanism of the ECU that is simply designed to reduce the load on the engine. But issues with the alternator can also lead to incidental failures of the transmission system at times.

For example, it’s common for alternators with internal voltage regulators to surge before they fail. When that happens, unwanted and excessive power flows through the electrical system in your vehicle.

alternator voltage regulator

The ECU can shift the power away from the transmission and make it go into sudden failure. Sometimes, the transmission can go into total failure and sometimes, it can get locked into certain shift points. That’s how a bad alternator can mess up the transmission in your car.

3. Other Problems

There are many other issues that are the direct effect of a bad alternator that can lead to transmission issues. For example, a bad alternator can cause a dead battery and that can ultimately lead to transmission failure.

alternator others problems

A damaged alternator can also cut the power supply to the ignition system in certain cases. So, there will be more unburned fuel going through the system and it can damage the catalytic converter. Even that can lead to transmission failure to bring down the pressure on the engine.

What Are The Symptoms Of Transmission Problems?

The transmission system is a vital component in your car that can sometimes be even more expensive than replacing your engine when it goes bad depending on the car you drive.

 transmission system

You should never ignore the warning signs of a failing transmission system. Here are the main symptoms of transmission problems that you should be on the lookout for:

i). Gears Slipping

The first sign of warning that you need to worry about is if your gears are slipping or lose traction when you’re driving. It’s a serious safety hazard if you have a slipping transmission system.

The ECU in your car tells the transmission when to shift between different gears. So, when the gears are slipping, it means that the ECU isn’t being able to send the signal properly.

ii). Noise From Transmission

If you hear a grinding, winding, or whirring noise from your transmission system, it’s a telltale sign that you have a damaged transmission system. It indicates that the mechanical parts within the transmission system have worn out and lost their lubricant.

noise coming from transmission

The first thing you need to check if you’re hearing any noise coming out of the transmission system is the level of transmission fluid. When your car is low on transmission fluid, it can easily explain why the parts are making noise.

They’ve lost the protection and lubricant they get from the transmission fluid. When they bump into each other in that condition, it creates that noise. This noise can also indicate that some components inside the transmission system have already been damaged.

iii). Vibrations And Transmission Failure

The transmission shifts between different gears in your vehicle will be smooth during normal operation. But if there’s a delay when you start driving your car or put it in reverse, both these issues indicate problems with the transmission.

When things get worse, you can experience your car shaking or grinding when you switch gears. It can be very little at first and increase with time. Pay attention to these symptoms before it’s too late so that you can immediately work towards fixing the damaged components.

iv. Check Engine Light Is On

The CEL in your car can be turned on due to a wide number of reasons. One of those reasons is when there are issues with the transmission.

check engine light is on

There are different sensors that can pick up when something is wrong with the transmission. The signal gets passed to the ECU and the CEL comes on.

What Else Causes Transmission Issues

Although a bad alternator can lead to transmission problems, it’s far from the most common reason behind it. There are many other things that you should check before you blame the alternator. Here are the most frequent reasons that cause transmission issues:

1. Leaking Or Low Transmission Fluid

Transmission fluid is just as important to the transmission system in your vehicle as our blood is to us. The main job of this fluid is to lubricate different components of the transmission by circulating through them.

adding transmission fluid

It transfers hydraulic properties to them so that the whole system can operate smoothly without any glitches. Transmission fluid also directs the heat away from the transmission components and helps them stay cooler. So, the transmission system doesn’t get overheated.

As you may have realized by now, your vehicle’s transmission system can run into all sorts of problems if there’s not enough transmission fluid. The components would grind against each other, start to be overheated, and it can eventually lead to total transmission failure.

Keep in mind that it’s not normal for your vehicle to run low on transmission fluid or for it to be leaking. The most obvious sign of a transmission leak is if you see red fluid lying on the floor of your garage. Be on the lookout for it.

As transmission fluid isn’t designed to lessen, running low on it is also a sign of a leak. Check the level of the transmission fluid with a dipstick. If you’re low, locate the source of the leak. It can be a faulty gasket or a leaking hose.

Replacing it will do the trick. Then, drain the old transmission fluid in your vehicle and put fresh fluid in it. Make sure you use the right type of fluid as recommended in your owner’s manual. Don’t ignore this problem if you want your transmission system to last long.

2. Overheating Transmission Fluid

With time, transmission fluid loses its ability to act as a lubricant for the different components within the transmission system. When that happens, you’ll notice the transmission fluid becoming dirty and darker.

You should never be getting a burning smell from the transmission system in your car. But when the transmission fluid starts losing its properties, the components within the transmission system get overheated and can cause that burning smell.

different levels of transmission fluid

The transmission fluid itself will also become overheated when the parts get hotter. It creates this self-destructing loop causing more damage to all the parts. Some of the components can start to break down and end up in the transmission fluid as sludge or debris.

You can check if this is the case in your vehicle by inspecting the transmission fluid with a dipstick. When you have the tranny fluid on the dipstick, transfer it to a paper towel and check its quality. If it turns out to be dirty, drain it, and replace it to solve the issue.

3. Clogged Transmission Filter

Just like oil filters prevent the debris in the oil from entering the engine, the transmission filter stops the dirt in the transmission fluid from getting into the transmission system. It protects the transmission fluid as well from getting contaminated with metal shavings from the gears and other debris.

With time, the transmission fluid will get clogged as more and more dirt will pile up on it. The required amount of transmission fluid won’t be able to pass through the transmission system when the filter is clogged.

clogged transmission filter

So, the system will be starved of transmission fluid and it can damage the internal components in the long run. Inspect the transmission filter in your car and replace it if it’s dirty. As a general rule of thumb, you should change the transmission filter after driving every 50,000 to 60,000 miles. 

4. Worn Out Gears

There are many parts in a transmission system including clutches, bearings, gaskets, pistons, metal drums, and more that makes it work together as an integrated unit.

transmission gears

With the help of a planetary gear, the transmission works by spinning one gear while the other stays stationary. It increases the ratio of different settings and allows you to shift into more gears.

In manual transmission systems, there are gear synchronizers. They help the new gear shift at the same speed as the gear you’re switching from. Because of them, you get a smooth and seamless shifting experience.

Any of these gears or gear synchronizers are a huge problem and can lead to transmission failure. The most obvious system of falling gears is when you hear a clunk from the transmission when you shift gears.

It can be costly to repair or replace broken components. But ignoring this issue can make the problem worsen over time and damage more transmission parts.

Take your car to a repair shop as soon as you can and do the replacement or repair procedures according to the suggestion of the mechanic.

5. Defective Clutch

When you notice poor clutch performance, it means the connection between the engine and the transmission has been disturbed. It can easily lead to damaging the different components in the transmission system.

defective clutch

There can be many reasons behind it. Mechanical error and hydraulic fluid leaks are usually the most common reasons that lead to it. You’d have to deal with this issue ASAP as well. More often than not, you’d have to replace the clutch and also fix the underlying reason behind the issue.

How Can You Avoid Transmission Issues

Transmission problems are terrible to deal with. So, it’s a good idea to take care of your vehicle’s transmission system as much as you can to avoid these issues. Here are some tips you can follow to keep your car’s transmission in good health:

1. Regular Inspections

The most important thing you need to keep in check to prevent transmission issues is transmission fluid. Be sure to check it at regular intervals. You can identify problems with the transmission system quickly if you do that.

For example, now you know that dirty transmission fluid can lead to transmission problems. If you do frequent inspections, you can catch that problem ahead of time and immediately replace the transmission fluid. Doing so will prevent further damage to your transmission system.

So, regular inspections will always help you stay on top of things. Even if the components of the transmission system are giving out signs of wear and tear, you can easily identify them by looking out for the symptoms. You can take corrective actions immediately and prevent major damage to the transmission.

2. Maintain The Level Of Transmission Fluid

The absence of transmission fluid can make the components wear out. So, you should make sure that you always have sufficient transmission fluid in your vehicle.

checking the transmission fluid

Whenever you run low on it, refill it and seal the leak. The same goes for when the transmission fluid is dirty. Change the transmission fluid from time to time at the intervals recommended in your owner’s manual.

Besides that, make sure that you always use the right type of transmission fluid for your vehicle. Doing these things will ensure that your transmission system will be lubricated and it’ll last longer.

3. Stop Overloading Your Vehicle

If you shift gears too quickly, it can cause transmission overload and lead to transmission failure. Accelerating the vehicle out of nowhere, going up hills, and driving with a loaded vehicle can all cause transmission overload.

You can calculate the transmission overload on your car by multiplying the weight of your car by 10. For example, if your car weighs 5000 pounds and you’re driving through a 20% grade hill, the transmission overload will occur at 500 pounds.

car going uphill

Make sure that you’re aware of the weight you’re carrying to prevent transmission overload even by accident.

Knowing the weight of your car will be of huge help in calculating the overload. If you maintain that, you should have no problems with your internal transmission system anytime soon.


What is the connection between an alternator and a transmission system?

The alternator and the transmission system in your share a few cables. That’s how they are connected to each other and a bad alternator can lead to issues in the transmission system.

How often should you change the transmission fluid in your car?

The right answer to that question lies in the owner’s manual as all cars are different. But generally, you’ll find that many car manufacturers recommend changing it every 30,000 to 60,000 miles.

What are the most common signs of a bad alternator?

The main signs of a bad alternator include a dead battery, flickering dash lights, warning lights on the dashboard, noisy sound, and some electrical components not working properly.

Should you replace a car’s alternator by yourself or hire a mechanic to do it?

Having a mechanic replace your car’s alternator is always the safer option. But it’s also the more expensive one. So, you can replace the alternator on your own if you’re mechanically inclined and feel comfortable doing the job.


Can a bad alternator cause transmission problems? Hopefully, you’ve found the answer to that question after completing this guide. Remember to rule out the other issues that can also lead to transmission failure before you start thinking of the alternator as the main culprit behind the issue.

Follow the maintenance tips to ensure that your vehicle’s transmission system lasts as long as possible. Comment below to let us know what was causing the transmission failure in your case and how you solved it.

Note: You can also read our ultimate guide on can a bad alternator cause overheating.

About John M

John contributed as a technical head at an automobile company just 2 years after his post-graduation in Automobile Engineering. He loves to lead a free life, so he left his job & started blogging. Now, he does research on every automotive problem, part & product and seeks a better solution & best products & shares his findings with his readers to help them as well as to minimize their struggle.

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