Why Car Shakes When Driving Over 70 mph (26 Possible Causes)

Whenever a car shakes, it can make you feel very uncomfortable. Every driver needs enough comfortability to ensure safe driving, therefore, whenever you experience any vibration from your car, you should immediately diagnose and fix the problem.

There can be different reasons why car shakes when driving over 70 mph, such as out-of-balance tires, faulty brake system, starved engine, uneven tire wear, and so on.

There are basically many reasons why this can happen, and that is what we’ll be discussing in today’s post.

Why Car Shakes When Driving Over 70mph

There are many reasons why car shakes when driving over 70mph, but, here are the most commonly noticed reasons;

1. Out-of-Balance Tires

Whenever a car is imbalanced, it can result in car vibration at higher speeds, most notably, the 70mph range and have a cupped or scalloped wear pattern.

Hitting potholes, bridge expansion joints and curbs cause imbalanced tires, which results in steering wheel vibration through the seats and floor.

2. Misaligned Wheels

Hitting a pothole, for instance, results in misaligned wheels, which in turn causes car shakes when driving over 70 mph.

However, what will resolve this problem is proper wheel alignment, which involves the angle at which wheels hit the road.

3. Faulty Brake System

Vibration through the steering wheel due to sticky brake calipers and rotors become noticeable starting at 45 to 50 mph.

The shaking gets worse as you close in on 70 mph, which comes with a burning odor when you halt your car.

Therefore, you have to re-index the rotor one/two lug positions on the hub or replace them if excessively worn.

4. Worn Parts

Other components of your car can wear out overtime and cause vibration. These includes, shocks, upper strut bearings, ball joints, and tie rod ends.

You discover these worn parts during wheel alignment and needs replacement, especially the worn wheel bearings which make high-pitched whining or grinding noises and the tie rods that make car wheels oscillate.

5. Uneven Tire Wear

This can be a result of a broken belt or slipped belt which causes your tires to vibrate or bounce. Even new cars experience this issue, as poor-quality tires are likely to wear out faster.

To ascertain which tire needs replacement, drive in the shakes speeds, so you could feel the vibration source, and replace them if needs be.

6. Runout Wheel

When you experience shakes when driving over 70 mph, it can be as a result of a runout wheel, which means any part of a wheel or tire assembly that is imperfectly round.

This may include, tires with shifted or broken belts. It’s a dynamic problem that causes wobbling at slow speeds and excessive rattling at high speeds.

To diagnose this problem, use a tire runout gauge, off-car balancer or dial indicator, and check at the center of the tire wall, on a smooth rib for best results.

7. Low Tire Pressure

This also contributes to why your car shakes when driving over 60 mph, which is why, to maintain it, you need to always take a tire pressure gauge and inflator with you on any journey.

Raising the tire pressure about 3 psi above manufacturer recommendation in cold weather help to mitigate tire pressure drop and keep it within a favorable range.

8. Engine Starvation

Every car requires sufficient air, fuel and spark plug to properly function. The absence of the aforementioned will make your car jerk and shake, especially when driving over 70 mph.

Also, ensure that the fuel and air filters aren’t clogged or dirty, hence, constant changing will guarantee that the engine is never starved of the fuel or air it requires.

9. Shabby Suspension Components

Normally, car shakes occur within the range of 50-75 mph. But, whenever the shaking begins at a certain speed and subsequently gets worse, then its likely cause is the differential and suspension mounts.

If the damage to the suspension components become so severe, you could require a new car, rather than replacing or rebuilding the entire suspension system.

10. Overworked Powertrain

This produces a clicking noise while reversing. A bad CV axle shaft can result in shakes while braking.

Also, severe wear and abuse of your clutch, flywheel, gearbox, and especially, steering rack components cause a vibration when you hit 70 mph.

The above factors are the common reasons why a car vibrates when driving past 70 mph.

11. Resonance in the exhaust

Modifying a car comes with a lot of stress, literally. You’d need to change a few other components the moment you decide to tune/replace a stock component to improve your engine’s performance/response.

Exhaust resonance is the vibrating sound you may hear/notice when you’re driving at top speeds. This happens because the engine and exhaust system are “vibrating” at incompatible frequencies. To fix this, you need to tune up the exhaust system by adding a muffler or sound dampeners.

12. Incorrect Gasoline Octane

Put simply, using regular gas (83 or 87) in a vehicle that requires premium gas (91 -91) could cause some serious engine damage in the long run.

If your car is designed to run with high-octane fuel (Premium Gas), stick with that – the same applies the other way round (if the car is meant to use regular gas with low octane).

13. Engine Sludge

If there is sludge inside the engine, it’d restrict the performance of the engine, and over time, it could cause clogs, which is liable to cause an engine to vibrate at top speeds above 60 mph.

Fixing this is quite simple – clean out the sludge/buildup inside the engine; this can be done by using the right motor oil for your engine.

14. Poor Workmanship

The effects of poor workmanship cannot be overstated; if you had your car repaired by an unprofessional mechanic, chances are that the mechanic didn’t couple the engine parts as supposed, hence, you’re feeling that your car shakes at top speeds.

That said, if you had a mechanic work on your car recently – before the “Shaking” issue started, go back to the workshop and request that they re-check what they did.

15. Rough Driving

Well, if you drive rough, you’d have your car parked in mechanic workshops frequently for repairs. Rough driving can cause some of the drivetrain components to fall out of position; thus, causing the car to shake at certain speeds.

Other reasons why car shakes when driving Over 70 mph might include;

1. Resonance in the exhaust
2. Incorrect gasoline Octane
3. Engine sludge
4. Poor workmanship
5. Make of the vehicle
6. Rough driving
7. Bad CV joints
8. Excessive lifts
9. Failed spark plugs or spark plug wires
10. Disconnected air or vacuum hose
11. Make of Vehicle

Conclusion

As you can see, there are several reasons why car shakes when driving over 70 mph.

So as a driver, if you ever experience vibration on your car when driving at a certain speed, the best thing to do at that moment is to consult with your auto mechanic for proper inspection and fixing.

But if you’re good at fixing your own cars, then we’d suggest you carefully check your car for any of the possible causes mentioned here.

Remember that it’s not wise to continue driving your car whenever you notice any anomaly as this may lead to a more serious damage and possibly accident.