What would cause intermittent vibration while driving at highway speeds?

This blog will answer the following questions: what would cause intermittent vibration while driving at high speeds? Should you ignore the intermittent vibration and continue to drive?

What would cause intermittent vibration while driving at highway speeds?

The following factors can cause intermittent vibration while driving at high speeds:

• Wheels and Tires 
• Warped rotor
• Engine misfire 
• Propeller shaft and axles
• Shock absorbers
• Engine mounts

Let’s take a detailed look at all the factors and their remedies:

Wheel and Tires

A vehicle is connected to the road by the tires so if there are intermittent vibrations present while driving at highway speeds, the wheels and tires are the most prevalent cause. Tires not only provide the necessary traction for driving but also absorb the vibration on the road surface before they reach the shock absorber.

As the tire starts to get old the tire compounds lose their oils and it becomes hard. Hard tires transmit more vibration to the vehicle, especially at highway speeds of 70-80 mph. If there is uneven tire wear the vibration can be more pronounced.

Hence, it is recommended to replace the tires once every three to four years even if the tread depth is not near the minimum value. Similarly, if the alloy wheel is bent or there is excessive run-out; it causes intermittent vibration while driving.

The wheels and the tires must be balanced properly. If the tires are replaced, it is recommended to also perform wheel balancing. A bent alloy wheel can even rub against suspension components like control arms and suspension struts.

Car manufacturers specify the recommended wheels and tires combination for a particular model. If there are incorrect wheels and tires then intermittent vibration at highway speeds can occur as the tire can rub against the bodywork.

If the vibration is occurring after replacing the tires then check the tire and wheel size as it can be incorrect. Some rear-wheel-drive cars also have wider rear tires for better traction, wider rear tires must not be installed on the front wheel when a tire rotation is performed.

Warped rotors

If there are intermittent vibrations at highway speeds, the braking system of a vehicle is the next possible cause. All cars have hydraulic disc brakes and the brake discs or rotor is a crucial component in the braking system.

There can be four or two rotors in a car and even a single warped rotor can cause excessive vibrations. The vibration can become stronger under braking or remain intermittent at highway speeds.

Extreme heat is generated under heavy braking and it causes uneven surfaces on the rotors also known as warping. Excessive run-out or uneven wear can be checked with the help of a dial gauge.

Car makers also specify the minimum thickness of brake pads and rotors. The thickness of the brake pads is measured by a depth gauge and the thickness of the rotor is measured by a vernier caliper.

A warped rotor and its brake pads must be replaced even if the thickness is more than the minimum value. A progressive braking habit can help to prevent uneven brake wear, and cooling ducts for the brakes can also be installed if the brakes constantly overheat.

Engine misfire 

Intermittent vibration at highway speeds can be felt due to a combustion misfire. A misfire occurs when the air-fuel mixture does not ignite in the combustion stroke. It can be a continuous misfire or intermittent in nature.

Due to a combustion misfire, the engine can shake or vibrate. The engine mounts are not designed to dampen vibration due to combustion misfires. The intensity of vibrations can increase if there is a misfire in more than one cylinder.

The cause of engine misfire is incomplete combustion in the cylinder due to a fault in the ignition or fuel injection system. It can be repaired by replacing components of the ignition system or the fuel injectors.

Engine misfires can also cause the check engine light to turn ON in the instrument cluster and the performance of the vehicle is also affected. Hence, it is recommended to not drive the vehicle when there is an engine misfire.

Propeller shaft and axles

The power from the engine is transmitted to the wheels through propeller shafts and axles. If a propeller shaft is out of alignment, it will vibrate as the speed of the vehicle increases. The propeller shaft can even come in contact with the exhaust or the underbody aluminum shields and cause intermittent vibration.

The propeller shafts also have a universal bearing and flex plate. As the shaft spins rapidly, damaged bearings or loose flex plates cause the transmission and the vehicle to vibrate. The vibration can intensify as the vehicle reaches highway speeds.

Axles have constant velocity joints and any damage to the axle can bend it. Misaligned axles can touch the suspension components. If there are grinding marks on the axles or the axle boot is damaged, it must be replaced.

Shock absorbers

The shock absorbers are connected to the wheels and the body. While driving on rough roads or potholes, the shock absorbers can bend at the mounting points. As these components are out of alignment intermittent vibration at highway speeds occurs.

If a vehicle is frequently driven over rough roads the top bearings of the shock absorbers get damaged or loose. While driving abnormal noise can also come along with the vibration. Hence, it is worth checking the suspension system for bush cuts or bent shock absorbers.

Engine mounts

Intermittent vibrations at highway speeds are commonly caused by broken or very old engine mounts. If an engine is mounted in the longitudinal direction, there will be two engine mounts and one transmission mount. The mounts act as insulators between the internal combustion engine and the subframe of the vehicle.

The engines in hatchbacks and small cars are mounted in the transverse direction so there can be more than three engine mounts. Even if a single mount is leaking or broken, the entire drivetrain can cause intermittent vibrations in the vehicle.

Replacing the engine mounts is the only way to rectify the problem. Engine removal is not necessary to replace the engine mounts but a propeller vehicle hoist and hydraulic jacks are needed. So do not replace the engine mounts without proper equipment.

Should you ignore the intermittent vibration and continue to drive?

No, intermittent vibration should not be ignored and the vehicle must be inspected by a technician to identify the cause of the vibrations. If the repairs are not performed the vibrations can cause even more damage and lead to vehicle breakdowns.

If the vehicle is under standard warranty then the dealership can rectify the problem with zero cost to the customer. However, if there is accidental damage to the wheels and tires then the warranty claim can be rejected.

Conclusion

This blog explained the causes and remedies for intermittent vibration at highway speeds. The intermittent vibrations will become permanent if the vehicle is not repaired. The driver can lose control of the vehicle and cause an accident on the highway.