Droaning noise from middle to rear of vehicle after lift

I have an ole beater '91 that I was going to use as a trail rig. I installed a 3" lift and immediatelly afterwards, I hear a droaning / whining noise coming from behind me. Hard to pinpoint the sound. Kinda pass floorboard area, but could be further back - low resonence sounds are difficult to tell where it's coming from. I only notice it while accelerating, so I think that eliminates wheel bearings. I'm sure the noise is a result of the lift anyway, so bearings would be purely coincedental. My next guess is U-joint, but I've never had one go bad, have no idea what it sounds like, etc. Are they hard to replace? Any other ideas? It is a steady sound - no metallic banging, clicking, etc. Kind of a growl - haven't gone faster than 30 yet, so don't know if it gets any louder w/ speed, but it's noticeable from 10mph up.

[FONT=&quot]Check your u-joint angles and adjust them to specs. You will probably need angled shims for the rear axle to get both u-joints to have the same angle.

If the angle is great enough, an SYE and a new CV drive shaft may be what it takes to cure it.

Welcome to the never-ending chain of modifications. Once you change one thing, most everything else needs to be changed or adjusted to match.[/FONT]