I have read several threads regarding the "second" transmission filter in the cooling line somewhere. I have looked over all the lines on my 2003 GM and saw no signs of a filter. I am the original owner so I know that it wasn't removed ar some point.Where exactly is the inline filter located?

 

There are two (2) transmission filters on the 2003 Grand Marquis.
The internal filter is Motorcraft # FT-105 (use original gasket).
The in-line filter is Motorcraft # FT-183.