differential

Hello I'm looking to buy a police package crown vic. I've researched it a bit and i have one question I have not found the answer to. How Can I tell which differential the crown vic has i know they come w/ 3.27 or 3.55 and the 3.55 always includes posi and the 3.27 has posi it an option. I assume there are codes on a service sticker somewhere on the car. where is it located and what are the codes for the different gears and the posi(limited slip) option. also if anyone has any opinon or preference on the gears (or any other options i should look for before i buy), I assume 3.55 will be a bit quicker off the line but has a lower top end. Thanks to all who reply!!!!!!!!!!!

I have crown vics with 3.27 and 3.55 the ratio is so close its hard to tell the differance. The axle code is on the drivers door sticker. Different years use different codes. See link below.
http://moldyrabbit.com/liquid/data.html




Hello I'm looking to buy a police package crown vic. I've researched it a bit and i have one question I have not found the answer to. How Can I tell which differential the crown vic has i know they come w/ 3.27 or 3.55 and the 3.55 always includes posi and the 3.27 has posi it an option. I assume there are codes on a service sticker somewhere on the car. where is it located and what are the codes for the different gears and the posi(limited slip) option. also if anyone has any opinon or preference on the gears (or any other options i should look for before i buy), I assume 3.55 will be a bit quicker off the line but has a lower top end. Thanks to all who reply!!!!!!!!!!!

I assume 3.55 will be a bit quicker off the line
Yes

but has a lower top end.
Not necessarily. I think the top speed (in overdrive gear) is drag-limited on these cars so the top speed will be about the same.
There will be a slight improvement in acceleration and responsiveness at highway cruising speed, but highway fuel economy will be very slightly reduced.