What additive for rear axle

[Coronet 14]

I sealed up the rear axle leak on my 8 3/4 axle. Now I have to add more fluid. I'm pretty positive it's a Sure Grip. What Friction modifier should I use. I didn't pull the center diff out to seal it just used RTV along the bottom and half way up the sides. Just have to add 90 weight to bring the level up. So I will have to add the friction modifier Thanks

 

[snakeoil24]

Ford Dealer for Friction additive. or order the Dana Spicer if it really is a dana Clutch sector.

 

[hunt2elk]

I use the Mopar friction modifier sold at the local dealership.

 

[DALTON]

I was about to ask the same question...I'm seeing a lot of different recipes for the Dana 60 with sure grip. Not sure what combo I am going with. Putting out 475hp at the wheels so I am thinking a heavier viscosity with some type of additive for the posi