Help - Differential Fluid question

I think i misidentified my rear differential as limited slip. I thought if i did NOT have locking diff, that i had LSD by default, but that isnt true is it? It can be lock, LSD, or open? The sticker on rear diff is marked "C3" and I think LSD is "C6"? 2005 Tacoma 4.0 4x4 with manual 6 speed.

I've already drained and added 3 quarts of Mobil 1 75-90 LS http://www.mobiloil.com/USA-English...bil_1_Fully_Synthetic_Gear_Lube_75W-90LS.aspx

AND a 7oz tube of "Trans-X Posi-Trac" LSD oil additive http://www.crcindustries.com/hd/content/prod_detail.aspx?PN=402508&S=N


Now what? Am I ok? Do i need to drain again, and refill with just the mobil 1?

I've drained the front also (4x4) but have not filled it yet. What do i do there? Additive or not?

Fortunately, i have another vehicle so it can sit until I know for sure, but id like to finish tonight so quick response is appreciated.

 

I don't think the additive will hurt...I wouldn't drain it.

No additive in the front.

 

Thanks! I also called a friend who used to be a yota tech. He said no problemo. LSD additive is necessary for the clutch packs on an LSD but not a problem adding it in this case.