High speed vibrations can be caused by many things on your car. Today I am going to touch on a few different reasons your car could be shaking.

Identify where the shaking is coming from.

The first thing we need to do is identify is what is happening during the shaking. Is it shaking when you brake? Is it shaking when you are pushing on the gas and not when you let off? At what speed does it happen? Does it shake when trying to accelerate? The answers to these questions will help pinpoint where to look so find the cause of the shake.

Is it shaking when braking?

Shaking at high speeds when you brake is an indication of a brake problem. It usually means that the Brake Rotors are out of round and when you apply the brakes you feel it. The shake will only happen when you apply the brakes. If you feel it in the steering wheel it means the front brake rotors are the issue. If you feel it in the seat it means the rear brakes are the issue.

Is it shaking while you are trying to accelerate and feel like it lost power?

If it is shaking while you are trying to accelerate it usually means you have an engine issue. A typical shake that happens at this time is usually an engine misfire. This misfire could be caused by a bad ignition coil, a bad spark plug, a fuel system problem, or an issues with the engine mechanically. If you keep driving the car while this is happening it may cause more damage to the car. Having this looked at should be a top priority.

Does it shake when you are accelerating and has not lost power?

This shake is one that could be a few things but the major culprit is usually a drive line problem. These issues are caused by worn CV Axles and Driveshafts with bad U-Joints. The shake usually occurs while accelerating hard up to highway speed then stops. The shake may come and go and seems to have very little consistency. Checking out the Driveshaft U-Joints and CV Axles is very important because if they break they usually cause a lot of damage because they are spinning at very high speeds.

Another thing that can feel the same as a bad U-Joint or CV Axle is worn suspension. Loose Tie Rods, Ball Joints, Bushings, or other worn suspension can cause a shake because the play allows the wheel to move side to side without input from the steering wheel. This should be corrected immediately because if left go it may cause an accident when it completely fails.

At what speed does the shake start?

If your car starts to have a shake around 30mph and runs ok and it keeps shaking all the way up to highway speeds you probably have a tire balance issue. This issue always gets confused with and alignment problem. Alignments very rarely cause vibration issues. Tire balance issues are common though because as a tire wears it can lose balance. Tires can also be an issue if they have an issue with the internal structure of the tire. When this happens balancing the tire may not work and the tire may need to be replaced.

Does the vehicle start to shake around 40mph on the flat and does not shake when going up a hill?

This is a fairly new issue we are running in to. It almost sounds like you are going over rumble strips when it happens. This is usually caused by a failing motor mount. A lot of new cars have a gas saving feature where it shuts off part of the engine while at a steady cruise. When the engine shuts of cylinders of the engine it uses an electrically powered motor mount to remove excess vibrations from the engine. If the engine mounts fail it causes a rumbling sound and feel throughout the car.

These are a few of the major things we see that can cause vibrations at highway speed. The easiest way to help your mechanic find the cause of the vibration quickly is to have a good description of when the shake happens. It will help them reproduce the issue helping them fix it quicker and saving you money.