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Have Valvoline 75w90 Limited Slip gear lube, says it already has friction modifier in it, but I see some adding additional modifier to these LS gear oils.
What is the consensus, is the amount of friction modifier already in the lube enough?
I recently changed the diff fluid in my Dad's C6 and used Valvoline 75W90 with no extra juice, no problems . After changing be sure to do several slow figure 8s in a large parking lot to get the new lube into all of the clutch packs.
Diff Gear Lube Change, Add Friction Modifier?
. After changing be sure to do several slow figure 8s in a large parking lot to get the new lube into all of the clutch packs. 
