True, the differential mount doesn't have a huge effect but it depends on how much we are talking about here. There are other components to take note. Usually, you will have other indicators.

Rear Differential Mount
Rear Subframe Mount Bushings
Rear Trailing Arm Bushings

Both the Subframe and Trailing Arm Bushings will give tire wear and a lot of looseness in the rear of the car. The Trailing Arm Bushings can be hard to detect how much wear they have. Even the slightest movement can indicate severe wear.

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Sam

84 300SD 350K+ miles ( Blue Belle )