Gear Oil for Diff Question

[new scouter]

1980 Scout II - 345 / 727 / D44s

I'm planning to drain, clean and refill the differentials this weekend. Will use Valvoline Synthetic 75W-90 Gear Oill to refill.
Question is with LS do I still need the additive or is it already in the oil?? Reading the label, the oil says
"•Contains special additives to reduce chattering in limited-slip differentials
•Recommended for (conventional and limited slip) manual transmissions where an API GL-5 or MT-1 fluid is specified"

If I do need to put the LS additive in, is there a particular kind/brand that you would recommend?
How much additive is required when filling the differential - 4oz bottle?

Thanks!

[Will Marsh]

IME the Valvoline Synthetic GL5 has enough friction modifiers in it to support the claim that you don't need to add any more in an IH Powerlock or Tracklock differential.

I'd change it as you intend to. If the clutches chatter, add an ounce or two of LS Additive. Otherwise, don't worry about it.

HTH,

Will Marsh

[new scouter]

Thanks for the advice!

-Michael