F150 Limited Slip Chatter

[My442]

My 1999 F150 has bouts of chattering with the limited slip. When this happens, I need to add a bottle of the limited slip additive.

It seems that the additive lasts about 12 months.

Any ideas?

I am running Mobil 1 75-90 synthetic and the Ford additive.

 

[Burbanite]

Check and see if Mobil makes an additive for their 75W-90 synthetic. I know that Amsoil makes an additive for all their synthetic axle lubricants but I am not sure about Mobil. It is possible that the Ford additive is not compatible with the Mobil 1 Synthetic lubricant in your axle.

 

[Schmoe]

I think Redline and Amsoil don't require additive. "I think"

 

[Dick in Falls Church]

AMSOIL gear lubes are formulated so as not to require additives. In over 25 years, I can recall 3 people who did add additives. Of course, 2 of them didn't drive in figure 8s after the changeover.

AMSOIL markets the additive for those who want to throw a bandaid at the fluid they either have in or put in.

 

[flathead6]

My442: This problem as you describe it is well known to some Tundra owners. The best thinking is that some differentials chatter easier than others. The solution is what you've done, adding the additive. Also, it seems to begin chattering again after about 30K miles. To settle mine down, I had to add 2 4oz. containers of the additive when I changed the rear end fluid. I, like you and your Ford, was one of the 'lucky' ones whose rear end chatters easily...but, maybe this means the clutches are tighter...therefore working better on icy roads or in the mud. I really do think you have nailed the solution to your problem.