Gears & Axles - 02 WS6 differential oil change?

Need to change the rear axle oil in 3.23 ratio.
What type dif is stock in a 02 WS6?
Gears only or clutch type?
Use additive with std gear oil, or synthetic only?

Read dozens of post here, and totally confused.
They talk about what they use...but don't say what type gears they have, posi or not!
Someone please clear this up for all up us. Thanks

Pulled the rear cover and its a Torson.
What type gear oil to re-fill with?

SAE 75W-90, I prefer Royal Purple. Lots of people use Mobil 1 Synthetic Gear Lube. And you'll need a bottle of GM rear differential additive.

here's a link to torsens' faq page

http://www.torsen.com/general/general_faq.htm

Some say use dino,,, and you wont have to use additive as it will run quieter..... i just changed mine and used mobil 1 ,,,75w90 and no additive... and i also have the Torsen style posi... my next change im going to use redline,,, ive heard nothing but good things about there lube,,, but i didnt have the time to wait for a mail order,,, if you do a search on here you will find treads on this topic...