Low vibration on vehicle

74000 miles new rims - new tires - slight vibration so had tires rotated and balanced - checked out ok. Recently while driving on wet pavement I let up on the gas and noticed the vibration let up and disappeared - gave it gas and it came back - I'm about to change the rear u joints - I figure they hang down the lowest and probably wear out first - what do you think?

Tom

Yes! Change the all u-joints on your rear shaft. Could also be your rear end gears or pinion bearing going out.