bad vibration

[ndh]

i've got a really annoying vibration that seems to be coming from the rear of my truck, i feel it the worst in 2nd and 3rd gears but also at high speed. i had the wheels rotated and balenced and it made no difference....also i jacked it up yesterday and turned the wheels by hand and visually inspected everything and i just can't see or feel anything unusual or out of the ordinary. any ideas? could it be a wheel bearing or maybe a u-joint?

thanks for all your help!

[cdnsarguy]

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1994 F-250 XLT 4x4, Xtra-cab, longbed

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Check the center hanger bearing and look hard/feel for wear at the universals. Mark all parts for alignment BEFORE disassy, use a pin punch or mechanics pen etc.......