Rear End Friction Additive Question

[112motorsports]

So I changed my rear end fluid a few weeks back and used Mobil One 75-140 and I did not add any friction additive to the oil. The oil has about 1500 miles on it, and when I first changed it all seemed well. However it has seemed as of late it needed the friction additive added to it. So I added 1 oz at a time and after the entire 4 oz Motorcraft bottle everything seemed back to normal. However it has gotten worst back to the hopping feeling when you crank the wheel had to one direction and stand on it. I don't know what to do, drain it and re fill it or just let it roll. Any help would be greatly appreciated. Thank you for your time.

[NYC F-350]

Originally Posted by 112motorsports

So I changed my rear end fluid a few weeks back and used Mobil One 75-140 and I did not add any friction additive to the oil. The oil has about 1500 miles on it, and when I first changed it all seemed well. However it has seemed as of late it needed the friction additive added to it. So I added 1 oz at a time and after the entire 4 oz Motorcraft bottle everything seemed back to normal. However it has gotten worst back to the hopping feeling when you crank the wheel had to one direction and stand on it. I don't know what to do, drain it and re fill it or just let it roll.

Add some more friction modifier. One ounce at a time until the chatter stops. Give it a hundred miles or so between adding more. You need to find the balance of just the right amount of modifier. Too little and you get chatter, too much and the limited slip will not operate properly. Nowhere does it say to only add 4 ounces to Mobil1, that is the standard additive mixture for the Motorcraft synthetic diff lube. If you use any other fluid you may need more or less, depending on the formulation.
Although, I have never heard of having to add any modifier to Mobil1, ever. You might have a clutch-pack issue where it has worn out.
Did you change the spring or restack the clutches?