Mysterious Vibration

[sparks]

I have a vibration at 50 mph in my '97 Defender. It's felt strongest through the steering wheel, but it's evident in the floor, etc. to a lesser degree. It comes in waves, slowly building up then fading out completely in about a 5 second cycle, followed by 5 seconds of no vibration, then repeating.

I recently replaced the differential, all the U joints, balanced and rotated the tires, and had the front end aligned, but still it persists.

Any ideas?

[mongoswede]

I have a vibration at 50 mph in my '97 Defender. It's felt strongest through the steering wheel, but it's evident in the floor, etc. to a lesser degree. It comes in waves, slowly building up then fading out completely in about a 5 second cycle, followed by 5 seconds of no vibration, then repeating.

I recently replaced the differential, all the U joints, balanced and rotated the tires, and had the front end aligned, but still it persists.

Any ideas?

check to make sure your lug nuts are all tight. Could be a tire balance issue. One way to rule things out. Drive up to 50 mph and the top of a hill. When you start going down put the truck in neutral and see if it still does the vibration. If its still there suspect tires or driveshafts.