This may not be the case, but my 2002 2.5 CRD has a vibration (in kph alas) between 65-85kph and again between 100-110kph (very loud drone from below the vehicle). Diagnosis: Worn rear universal joint.
To eliminate this get under you Jeep try hold the shaft coming out of the gearbox tight while trying to wiggle/twist the propshaft. If you notice play on the joints, you have an issue. Repeat the same for the rear joint. If you rotate it without holding it, you will get rotational play, but no up/down/left/right movement. Anyway, you will see it if it is worn, it is pretty obvious.