If you mean the arm between the shifter and the transmission, it should be just above the exhaust, right below the shift ****, near the top of the transmission tunnel. At least, it is on a 2005 coupe, so I imagine it's the same on the 2008 sedan with the same Jatco unit.

Just stand outside the car and draw a line straight down from the shift ****; the linkage starts just above the exhaust on that line. Thinnish black rod.

 

 

 

This diagram will give you some idea: http://www.infinitipartsdeal.com/par...agram=349_F001