Assuming the new tires are any good, it sounds like whoever replaced the differential didn't align the rear wheels properly after they did the job. Replacing the diff will alter the alignment.

Out of curiosity, why did the diff need replacement? Is this a common problem? Is mine next?

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Lenny

There are only three sports: bullfighting, motor racing and mountaineering; all the rest are merely games. --Ernest Hemingway

'10 GL550/'04 BMW 545/'99 BMW 323/'98 ML320/'87 VW GTI (race)