Look at the plaque on your firewall. It'll show the car's transmission model number. If it says "RE4F04A" you have an open differential. If it says "RE4F04V" you have a limited slip differential. LSD is different than locking diff, though. No Maximas have locking diffs.
-The MinisterofDOOM 
|The Q of DOOM| - |The Maxima| - | Hear my Q!|
4.08 VLSD, NICO 8-way ECU, full exhaust with custom headers,
Tokico Blues with Eibach springs, Stillen FSTB, 20mm RSB, 255 rear rubber.