98 Ford F150 rear end vibration

My 98 Ford F150, 4x4, V8 (96k miles) is having some vibration in the rear end. The transmission changes smoothly and drives fine. The vibration feels gets louder the faster you go, but when let up off the gas pedal the vibration is not noticeable. Is has progressively got worse and feels like gears/bearings are not necessarily grinding but it has resistance. Not sure if it is transmission issue or gear, joint, drive train issues. thanks

jeff
Jeff; Take a close look at the u-joints and carrier bearing, if it has one. You may have to pull the driveshaft out to be certain. U-joints can 'bind' to the point that you can't feel any play, but once you take the shaft out, you'll be able to tell if they are moving both directions smoothly. Ford diffs. aren't know for problems, and usually, the noise/vibration will be on decel rather than accel.
Loren
SW Washington Loren , thanks for your quick response. I am hoping it is what you diagnose instead of a transmission. Thanks

Jeff (TN)
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