Q: My 2005 Ford Explorer XLT AdvanceTrac suddenly developed a front-end vibration problem that is at its worst at about 70 mph, less so at 3-4 mph faster or slower than 70. The vibration may be coming from the driver's side. I say that only because the driver-side outside mirror vibrates at that speed too, where the passenger side doesn't. I had the wheels balanced by a local tire store and it didn't help. I haven't taken it to the dealer yet, because I don't want to mess with the runaround unless I have to.

A: If your Explorer is a 4x4, Ford Technical Service Bulletin 05-16-4 explores what it refers to as a vibration/drone/boom at 55-75 mph. This condition is experienced only in third gear with overdrive off, and is not felt through the steering wheel: It's more in the seat of your pants. The TSB covers the 2002-2005 Explorer, Aviator, and Mountaineer, and the fix is the installation of a "premium balanced" driveshaft (whatever that means). If you have a 4x2 Explorer and the vibration is felt in the steering wheel, that indicates it's coming from the wheels and/or tires. And even if wheels balance correctly, they still may cause a vibration or shimmy, especially at high speeds. There may still be excessive wheel and tire radial run-out. The dealership has special equipment to measure and correct radial run-out. It involves breaking the bead and rotating the tire to a position on the wheel where the run-out of each will counteract each other. This is referred to as match mounting. Another common vibration complaint is due to flat spots on the tires caused by the vehicle sitting for long periods of time. It can take up to 200 miles of driving to smooth out the flat spots and eliminate the vibration, but this is considered normal. If the problem is not felt in the steering wheel, and is a true driveline vibration, it can be caused by a loose U-joint, unbalanced driveshaft, or improper driveline angles. The techs at the dealership can also evaluate a driveline issue if it comes to that.

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