Most Likely Causes:
* Tire Balance: This is the most frequent cause. An imbalance in one or more tires will cause a vibration at highway speeds. This is easily checked and corrected by a tire shop.
* Tire Rotation: Uneven tire wear can exacerbate balancing issues or even create a shaking problem on its own. Rotating your tires might temporarily alleviate the problem if the wear is uneven.
* Bent Wheel(s): A bent rim, even a slightly bent one, can cause a noticeable shake. This is harder to detect visually and requires a wheel balancing machine to confirm. Hitting a pothole is a common cause of bent wheels.
* Worn Tire(s): Severely worn tires, especially with uneven wear, can contribute to vibrations. Check the tire tread depth and look for any unusual wear patterns.
* Wheel Bearings: Worn wheel bearings can cause a vibration, though it might be more of a rumbling or humming sound than just a shake. This is a more serious issue requiring replacement.
Less Likely, But Possible Causes:
* Suspension Components: Worn-out ball joints, tie rod ends, or control arm bushings can contribute to steering wheel vibrations, but this is less likely to be isolated to a specific speed range. This often presents as a more general instability or wandering.
* Driveshaft Problems: Although less common, a damaged or unbalanced driveshaft *could* cause a vibration. This is usually accompanied by other symptoms like clunking noises.
* Brake Problems: Warped brake rotors can cause vibrations, particularly when braking, but could sometimes contribute to a subtle shake at speed.
Troubleshooting Steps:
1. Visual Inspection: Carefully examine your tires and wheels for any obvious damage (dents, bulges, uneven wear).
2. Tire Rotation and Balancing: Take your vehicle to a tire shop and have your tires rotated and balanced. This is the first and most important step.
3. Wheel Inspection: If the balancing doesn't solve the problem, ask the tire shop to inspect your wheels for bends.
4. Professional Inspection: If the problem persists after balancing and wheel inspection, take your Caravan to a mechanic for a thorough inspection of the suspension, brakes, and driveshaft.
Important Note: Driving with a shaking steering wheel can be dangerous. Don't delay addressing this issue. The most likely cause is a relatively inexpensive fix (tire balancing), but ignoring it could lead to more serious and costly problems.
