Can A Bad Transmission Cause Engine Problems? (Explained)

This is probably one of the topics that we get commonly asked about. Is it possible that a bad transmission can actually lead to engine problems and damage? After checking up on the topic in Google, we quickly realized that quite a lot of people were asking themselves these questions. We decided to answer how a bad transmission can in fact cause engine problems and what and how exactly it happens.

Can A Bad Transmission Cause A Rough Idle?

While it is very unlikely that your automatic transmission is responsible for the rough idling of your engine, it is possible in theory. The mechanic that we regularly consult for these articles confirmed that he has seen a few of these cases in the 20+ years he worked as a mechanic.

The only way a transmission can lead to engine problems is through vacuum leaks or malfunctioning vacuum modulators. Certain automatic transmissions use engine vacuum to determine the throttle position and consequently, time the shifts. If there is a vacuum leak in that connection, the idle of the engine can be affected due to a faulty transmission component. Additionally, a faulty transmission vacuum modulator (TVM) can also be the reason behind an unsteady engine idle. A leaking or a blown TVM can cause the engine to stall, it impairs the acceleration and can lead to the transmission fluid being sucked into the engine. Replacing the transmission vacuum modulator and inspecting the vacuum lines is not complicated or expensive, so it is worth inspecting them.

Can Low Transmission Fluid Cause Rough Idle?

No, there is not even a theoretical possibility that a low level of transmission fluid is impacting the idling of your car. If your engine is having problems with idling, we suggest you inspect the spark plugs, coil packs and fuel injectors first.

Can Bad Transmission Fluid Cause The Engine To Misfire?

We saw this as a common query in Google and decided to consult our mechanic advisor who laughed at the question. 

No, bad transmission fluid will not cause the engine to misfire. However, certain transmission problems like torque converter lock-up can feel like your engine is misfiring when it is in fact a transmission problem that is causing the misfiring type symptoms. Old, low or worn-out transmission fluid will eventually lead to serious transmission problems but it cannot spark sudden engine problems like misfiring. Fuel injectors, spark plugs, and coil packs on the other hand are common culprits behind a misfiring engine.

Can It Cause the Check Engine Light To Come On?

Yes, transmission problems can definitely be the cause for the “check engine” warning light. Although it is true that certain cars do feature a separate “check transmission” warning light, it is more common that your car will trigger the “check engine” warning light in case of transmission problems. 

A check engine light can ignite because you have low transmission fluid because your transmission fluid is overheating, etc. However, it is important to know that most cars will not specify where the problem lies as the “check engine” light illuminates. Certain cars will provide error messages on the infotainment screen but in most cases, you will need professional diagnostics to determine the real reason behind the warning light.

It is also important to know that you should never rely on your car informing you about low transmission fluid or other transmission problems. Serious damage and other symptoms (slipping, hard shifting gears, jerking)  will indicate problems a lot sooner than your car will trigger the warning light. So be mindful of any changes in your transmission’s behavior and take care of the problem immediately.

Can It Cause The Engine To Overheat?

The first and more common way is by wrongful gear selection. If you drive on a highway and your automatic transmission does not shift into a higher gear to achieve lower RPMs, it may overheat your engine as it over revs for an extended period of time. The problem here is in both the driver and the transmission. There is surely an underlying reason why the transmission is not shifting into the appropriate gear. And the driver is also at fault if he does not recognize that the engine is over-revving.

The same thing can happen when climbing steep hills, the transmission should shift into the lowest gear possible to prevent the strain on the engine and prevent the overheating of both the transmission and the engine. The cooling system of an automatic transmission is separated from that of a car which means there is no possibility that an overheating transmission also impacts the engine.

Can A Bad Transmission Cause The Car Not To Start?

Yes, there are multiple mechanisms by which transmission can prevent the car from starting. This is true for both modern manual transmissions and automatic transmissions. A faulty transmission control unit, a bad brake light switch and a bad transmission range switch are all transmission components that can prevent the car from starting. 

To find out the reason why your car will not start, professional diagnostics are needed. The diagnostics tool will definitely show up the error codes responsible for the problem at hand.

Can It Cause Stalling?

Yes, a bad transmission, both manual and automatic can make the car stall. With regular automatic transmissions, a failing torque converter can have problems engaging and disengaging which can make the car stall unexpectedly. Heavy slipping of an automatic transmission can also lead to car stalling. As we already mentioned vacuum leaks or a malfunctioned vacuum modulator can also lead to erratic engine operation. This means that a vacuum-related issue can also be a reason why your car is stalling.

The problem here is that diagnosing the issue behind stalling is very difficult to do without professional diagnostics. There are so many components that can contribute to stalling that it is almost impossible to diagnose the problem at home.

Can It Cause The Engine To Burn Oil?

The answer is no, no transmission out there can cause the engine to suddenly start burning oil. However, as we mentioned before, an automatic transmission can face problems by not engaging higher gears at high speeds which can lead to over-revving the engine. Over-revving can lead to an increased engine oil consumption and stress on the internal parts of the engine which can with time lead to engine oil consumption. 

Can Driving With A Bad Transmission Damage The Engine?

Yes, definitely. A bad transmission can put additional stress on the engine which can lead to increased wear and tear of engine components. It is crucial that both components, the engine and the transmission are in perfect working order to avoid any kind of problems with either the engine or the transmission.


We hope that providing these answers to what seem like weird questions can alleviate your worries. The answer is yes, many Bad Transmissions can in fact Cause Engine Problems. We all know how stressful it can be to deal with car problems and have no support until your mechanic is available. One thing that we have to point out here is that you should keep in mind that no serious or hidden problem can be or should be diagnosed at home. Before you get depressed about what is wrong with your car, take the time to visit a mechanic and find a suitable solution to the problem as you conclude. 

I had a transmission vacuum modulator causing trouble with both my transmission and my engine and I had no idea what in the world was going on. I could already see the insane repair bills that were waiting for me. I could not sleep. In the end, it turned out that my mechanic simply replaced 1 vacuum line and the vacuum modulator. Both of these components cost me less than 70$ and I drove off the mechanics’ lot with all the issues solved for 100$. 

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