2nd Gen Non-Engine/Transmission Friction Modifier Questions

[Turbo Terry]

I have a 1999 2500 with 150 k. Since new I have used Mobile Syn 75 -140 gear grease front and rear. I have Mag Hytec covers also. I haul a 2500 lbs slide in camper and sometimes pull a 1500 lbs trailer . I also have Firestone airbags Rancho adjustable shocks and a BD exhaust brake to help stop it all. I have changed grease about 5 times or every 30 k? I have never had a any issues and Mobil although expensive has done the job for me. Now I just bought some new Mobil Syn 75 140 and it has is limited slip friction modifier already added to it. Is this ok to use in the front differential ? Also I used to use Mopar friction modifier (two 4 ounce bottles in the rear differential). Should I still add those or can I put to much modifier the rear end?? I would hate to screw this up as it has work well for me all these years. I need your thoughts on this thanks.

 

[SAndreasen]

The friction modifier won't hurt the front diff and I wouldn't add any more to the rear diff if the oil already has it added