How do I identify what gear ratio I have?
 

I have a 98 Grand Marquis with traction control.
I read somewhere else that guys that own crown vis with a 273 rear end get better gas mileage than crown vic with a 373 rear end.

If this is true and I have the 373 can I swap the gears without changing the entire rear end housing?

Im only interested b/c my grand marquis is horrible on gas. I have always been a fast driver but with this car I have learned to drive very slow and slow take off all that gas saving stuff yet my gas mileage still sucks.
My car is in very good shape with no mecanical problems.
Thanks in advance for your input.

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