I am getting mixed information on this from a Ford Dealer and from a Mercury dealer. I have a 97 Grand Marquis. I just bought it and I was thinking about doing a rear diff service (drain and refill). The owner's manual says, to do it at 105,000 miles. The Ford dealer says it does not have synthetic fluid and should be done every 30,000 miles. The mercury dealer says it does have synthetic fluid and therefore should be done at 100,000 miles. The car only has 77,000 miles and it is not making any noise. At another point in the owner's manual it says, the rear diff should not serviced AT ALL as in NEVER unless it has been in water.
Any ideas?
Any ideas?
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