Any differential work is going to require you to refill it with Mustang gear oil & friction modifier. Gear installs, axle swaps, traction-lok rebuilds, differential rebuild, and any other projects that require you to remove the differential cover are going to require more gear oil and friction modifier. Get the all in one kit from Late Model Restoration which includes two bottles of Royal Purple max-gear oil and one bottle of Ford Performance friction modifier. The perfect amount to get your rear end filled back up while virtually eliminating gear and bearing wear, reducing temperatures, and giving your Mustang a smoother operating differential.
