I think it's safe to say the differential is not the problem, and that the mechanics you consulted are guessing.
I suggest you work methodically through the possible causes, eliminating each in turn, and hope to arrive at a definite or at least probable cause. Start with the tyres as mentioned by Magnet in 2022, then wheel bearings, rear tracking, CV or universal joints, prop shaft pillow bearing.
The tyres are the most likely culprit. Look for mis-matched tread patterns, wrong pressure, and balance.