[Beav]

Try inserting the FWD fuse and driving it a bit. If the problem goes away you have an issue to the rear, if the vibration remains look forward. Inner cv joints can cause vibration under accel/decel conditions without noticable hi-speed vibration. Driveshaft u-joints can also create this type of vibration under load, rarely during decel and are almost always accompanied by squeaky noise during accel. Or at least a good 'whang' when placed in gear from park/neutral or a change of direction.

Differentials rarely cause vibration at low speed, unless they have been making hi-speed vibrations/noise for a long time. Typically, differential noises come from worn/damaged bearings. Mesh noises occur either a) immediately following a rebuild or b) after bearing damage has occured and allowed the mesh to change.