| There is a little 'tag' on the diff itself. It should have some numbers like 'S346....' on it. If it begins with an 's', its limited slip, followed by the ratio.....so the 'S346' used for example would be a limited slip 3.46 diff. I don't know about the 540i for sure, but I am pretty sure its an S3.43? don't know for sure, but you could jack up the car and eliminate all the guessing.
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