Grand cherokee vibration.

I have recently had my 98 grand cherokee front differential overalled.Initially new bearings and planet gears were installed but the garage filled it with contaminated oil and consequentially the whole thing had to be renewed including new bearings,crown wheel and pinnion. It now vibrates very slightly. As you approach 70mph it becomes noisy ,sort of resonant and you can feel the vibration slightly in the car even the seats. I thought maybe propshaft balance but the car was quiet and vibration free before. Any ideas please.

Did the same shop do the rebuild? I'd have to question their work after the contaminated oil incident.

Did the same shop do the rebuild? I'd have to question their work after the contaminated oil incident.
Yes they did. They were horrified and even showed me the oil analyst report. Do you have any idea what they could have done in rebuilding the axle that might cause the vibration?