Found this comment on red line gear oils
75W90 GEAR OIL - recommended for most street driven and racing differentials. Excellent performance in conventional and limited-slip units. Also for limited-slip manual transaxles which require a 90 WT oil. Contains limited-slip friction modifiers.
75W90NS - recommended for manual transmissions and non-limited-slip transaxles that recommend 140 WT oils. Can be used in racing limited-slip units to increase lockup and reduce wheel spin. Street-driven rear-wheel drive cars should use regular Red Line 75W90 or 80W140.
Looking for feedback on either version and any problems encountered like syncro issues.