You press down on the gas pedal. The car starts to go faster. You get up to around 40 miles per hour. But then your car starts to shake! This shaking happens when you are speeding up.
It does not happen all the time. Just when accelerating your speed goes from around 30 to around 40 miles per hour. Something is wrong with your car.
Several things can cause this shaking.
I outline the common causes of car shaking when accelerating at 40mph and effective solutions to address the issue.
Here’s why your car shakes when accelerating at 40mph:
1. Suspension problems
Issues within the air intake or exhaust systems can significantly affect a car’s performance, leading to shaking when accelerating and changing directions.
How suspension problems lead to shaking when accelerating at 40mph:
Worn-out Shocks or Struts: Shocks and struts are essential parts of a car’s suspension system that help absorb shocks from road imperfections.
When these parts wear out, they lose their ability to effectively dampen vibrations or movements.
This leads to excessive bouncing, vibrations, or a shaky ride, especially when driving over bumps, or rough roads, or shaking when accelerating at 40mph.
Broken or damaged suspension components: Damage to other suspension components, such as control arms, bushings, or springs, can cause instability in your car’s handling.
If any of these parts are broken or worn, it can result in uneven weight distribution or erratic movements, leading to shaking when accelerating at 40mph.
Misaligned or bent suspension parts: Misalignment or bending of suspension components due to accidents, impacts, or wear can affect your car’s steering and handling.
This misalignment can cause your car to shake when accelerating at 40mph.
Signs of suspension problems:
- Excessive bouncing or dipping when accelerating driving over bumps or uneven surfaces.
- Uneven tire wear, indicating improper suspension alignment.
- Steering wheel vibration or shimmy when accelerating at 40mph.
- Clunking or knocking noises when accelerating, going over bumps, or steering.
- A feeling of instability or a loss of control while driving.
Solution:
A qualified mechanic needs to inspect and address suspension issues. This involves addressing any signs of wear, damage, or unusual noises.
Related: Why is my car shaking when parked and driving (Here’s why)
2. Tire problems
A car during reverse can be caused by tire problems.
Tire issues can significantly contribute to shaking and pulling problems in a car, especially if the tires are not in optimal condition.
Car shaking during reverse can happen due to:
Uneven tire wear: when accelerating tires wear unevenly due to factors like improper inflation, misalignment, or lack of rotation, they develop irregular tread patterns.
This uneven tread wear can cause vibrations and shaking, especially when accelerating at 40mph, as the irregularities in the tire surface create disturbances in the smoothness of the ride.
Low tire pressure or imbalance: Tires that are not properly inflated or are imbalanced can also lead to shaking.
Low tire pressure can cause uneven contact with the road surface, resulting in vibrations or shaking felt through the steering wheel or the entire car.
Also, imbalanced tires, where weight distribution among the tires is uneven, can cause noticeable vibration when accelerating at 40mph.
Tire damage, worn tread, bald tires, or bulges: Worn tires or damaged tires, such as those with bulges, cuts, or sidewall damage, can cause shaking.
Bulges, often caused by impacts or internal tire damage, can create imbalances that cause vibrations when accelerating at 40mph.
Signs of tire issues:
- Uneven tread wear across the tire surface.
- Visible damage such as cuts, bulges, or cracks on the tire sidewalls.
- Vibration or shaking felt through the steering wheel or the car itself, especially when accelerating at 40mph.
- Steering wheel vibrations or shimmy, particularly during acceleration, braking which can also manifest when accelerating at 40mph.
Solution:
Seek the expertise of a qualified mechanic to diagnose and replace the damaged or worn-out tires.
Regularly inspect your tires for signs of wear and maintain proper tire pressure to ensure balanced tires.
3. Brake problems
A car that is shaking when accelerating at 40mph can also be caused by brake problems especially when accelerating the braking system faces certain issues.
Here’s how brake problems affect performance:
Uneven brake pad wear: when accelerating brake pads wear unevenly, one side might wear out faster than the other.
This uneven wear can cause an imbalance in braking force, leading to shaking which is noticeable when accelerating at 40mph and when pressing on the brakes now and then.
Warped brake rotors or drums: Warped brake rotors or drums can lead to vibrations or shaking during braking.
As the brake pads make contact with these uneven surfaces, it can create vibrations felt through the steering wheel or the entire car.
Stuck calipers or brake components: Calipers or other brake parts that get stuck or fail to release properly can cause dragging brakes.
This constant contact between the brake pads and rotors can lead to excessive heat build-up, resulting in vibrations, pulling, or a noticeable decrease in performance when accelerating braking.
Brake fluid issues: Contaminated or old brake fluid can lead to brake system malfunctions, affecting the brake’s ability to function correctly.
This can cause uneven braking pressure, resulting in your car shaking or shuddering when accelerating at 40mph, when accelerating applying the brakes.
Signs of brake problems:
- Vibrations or shaking are felt through the steering wheel or the car when accelerating and braking.
- A pulsating or vibrating brake pedal when accelerating you apply pressure which is a sign of warped brake rotors.
- Squealing, grinding, or squeaking noises when accelerating braking.
- Longer braking distances or decreased braking effectiveness.
- Brake pedal feels spongy or sinking to the floor.
Solution:
Have a qualified mechanic conduct a thorough inspection and diagnosis.
Regular inspection and maintenance of the braking system, including checking brake pads, rotors, drums, calipers, and brake fluid help to detect issues early on.
4. Worn engine mounts
Engine mounts play an important role in stabilizing the engine and minimizing vibrations transferred to the car’s chassis.
Over time, engine mounts can deteriorate or become damaged. When these mounts wear out or become damaged, they lose their ability to dampen the engine’s vibrations effectively, and more vibrations are felt inside your car’s cabin.
As a result, when accelerating you might experience noticeable shaking or vibrations due to increased engine movement and transmission of vibrations.
Signs of faulty engine mounts
- Excessive vibrations especially when accelerating, or when your car is idling.
- Clunking or thumping noises from the engine area as the engine moves.
- Visible movement of the engine, especially when accelerating shifting from “Park” to “Drive” or during sudden acceleration or deceleration.
- A misaligned engine or transmission due to failed mounts can lead to misalignment of other components, causing additional issues or wear on related parts.
Solution
A mechanic should examine the engine mounts for signs of wear, damage, or excessive movement and recommend the appropriate course of action, which may involve replacing the worn mounts to restore stability and reduce vibrations within your car.
5. Transmission problems
Transmission problems can cause a car to shake when accelerating at 40mph.
The transmission is responsible for transferring power from the engine to the wheels, and any problems within this system can disrupt power delivery and affect overall performance.
Problems can be caused by insufficient transmission fluid, a malfunctioning torque converter, or clutch problems.
Insufficient or degraded transmission fluid levels can cause inadequate lubrication and cooling within the transmission. This insufficiency can lead to rough shifting, and slipping gears, and ultimately cause the car to shake or shudder when accelerating at 40mph.
The shaking can also be caused by a malfunctioning torque converter. A malfunctioning torque converter responsible for transferring power from the engine to the transmission, can cause the transmission slipping or shudder.
In a manual transmission car, a slipping clutch due to wear or damage can cause a lack of power transfer, resulting in shaking or vibrations when accelerating.
Signs of transmission issues
- Shaking or vibrations are felt in the car when accelerating.
- Delayed or rough shifting.
- A burning smell or fluid leaks.
- Unusual noises.
- Unusual hesitation, slippage, or a feeling of the car struggling to maintain speed or acceleration can point to transmission trouble.
Solution
Diagnosing transmission problems requires a thorough inspection by a qualified mechanic to identify the specific problem.
Fixing these problems involves repairing or replacing transmission components with wear, damage, or faults, or a transmission flush or service to remove contaminants and improve transmission performance.
6. Exhaust system problems
A car shaking when accelerating at 40mph can also be caused by exhaust system problems.
Issues within the exhaust system can create back pressure or disruptions in the engine’s ability to expel exhaust gasses efficiently, leading to engine irregularities and shaking which is also noticeable when accelerating.
For instance, when accelerating the exhaust system encounters blockages or damage, it disrupts the engine’s efficiency.
This disruption leads to fluctuations in engine performance causing your car to shake or vibrate when accelerating as a result of the irregularities in engine function.
Signs of exhaust system problems
- Increased exhaust noise.
- Vibrations or shaking.
- Reduced power and performance.
- Strange smells like sulfur (rotten egg odor) from the exhaust, indicating issues such as a failing catalytic converter.
Solution
Have your car inspected by a professional mechanic. They can examine the exhaust system to check for blockages or leaks to identify the specific issue.
Related: Why is my car shaking and not accelerating (Explained)
7. Wheel alignment issues
Car shaking when accelerating at 40mph can also be caused by wheel alignment issues.
Improper wheel alignment can cause uneven wear on the tires. Unevenly worn tires can create irregularities in their surface, leading to vibrations and shaking which is noticeable when accelerating at 40mph or maneuvering at low speeds.
In addition to this, incorrect wheel alignment can result in certain areas of the tires having more contact with the road than others. This uneven contact can cause vibrations or shaking sensations as the tires roll during acceleration.
Misaligned wheels can also cause your car to pull to one side, especially when accelerating. This imbalance in steering can cause shaking as the tires encounter resistance due to the misalignment.
Signs of wheel alignment issues:
- Car pulling: A common sign of alignment issues is the car pulling to one side, even when accelerating attempting to drive straight on a flat road. This occurs because the wheels are not aligned correctly, causing the car to veer in a particular direction.
- Uneven tire wear: Misaligned wheels can cause uneven wear patterns on the tires. Visually inspecting the tires can reveal excessive wear on certain areas, such as the inner or outer edges, indicating alignment problems.
- Steering wheel off-center: If the steering wheel appears off-center when accelerating driving straight, it could signify alignment issues. A properly aligned car should have the steering wheel centered while driving in a straight line.
- Vibration or shaking: Improper wheel alignment can lead to vibrations or shaking, especially when accelerating or driving at low speeds, as the misaligned wheels cause uneven rolling and stability issues.
Solution:
Seek the expertise of a qualified mechanic to diagnose and adjust the angles of the wheels to the manufacturer’s specifications.
Regular alignment checks, especially after hitting potholes or curb impacts, can help prevent uneven tire wear and associated shaking or vibrations while driving.
Alignment adjustments ensure that the tires make proper contact with the road, promoting even wear and a smoother, more stable driving experience.
8. Axle or drivetrain issues
Car shaking when accelerating at 40mph can also be caused by axle or drivetrain issues.
Issues with the drivetrain components, such as worn CV joints or a failing differential, which are responsible for transmitting power from the engine to the wheels, can cause vibrations or shakiness, especially during driving at 40mph or turning.
Signs of axle or drivetrain issues:
- Vibrations or shaking, particularly when accelerating or turning.
- Clunking, clicking, or popping noises coming from underneath the car, especially when accelerating, turning, or shifting gears.
- Difficulty maintaining speed or power loss during acceleration.
- Uneven tire wear or unusual tire patterns indicate drivetrain-related problems.
Solution:
Seek the assistance of a professional mechanic to assess your car’s drivetrain and axles.