Could someone tell me what this additive is for? Is a particular brand better than others? At what interval should it be used?

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CG
F-250SD CC SB 4x4 5.4L 4.10LS, Superchip, Hellwig anti-sway, Rhino, Bilstein shocks

 

I believe the additive is called a "friction modifier". It is added whenever you change the differential fluid. The Dana people (F-350, F-450, F-550) recommend Mopar Friction Modifier (No, I don't wanna go there!)
I think they're all about the same. Since my truck came with synthetic differential oil, I'm not changing mine till it needs it. My LS works GREAT - when the RR starts to spin, I just push a little harder on the loud pedal and the LR starts working...
Enjoy!!

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1999 F-250 XLT Super Duty Crew Cab Long Bed
V-10, Automatic 4R100, 4.30 Limited Slip.
GVW = 6700# Towing Capacity = 13,300#
4 Wheel ABS disks + Reese 15K hitch
Dark Hunter Green. Ford Running Boards.
Grey Rhino-Liner. Captain's Chairs. CD+Tape
Polished Stainless Steel Wheel-well Molding http://members.home.net/jchartier/jnctrk.html


[This message has been edited by J-C (edited 08-16-1999).]

[This message has been edited by J-C (edited 08-20-1999).]

 

I don't know if it's different for 1/2 tons but there's a friction modifier that you can purchase from ford for ls. I had to replace my diff fluid after getting water in there threw the vent tube from offroading. I priced it out at ford, and it came to $250 canadian, so I obviously ended up doing it myself, so it came to about $120 canadian using a high performance synthetic gear oil. Has anyone re-routed there vent tube to prevent water from getting inside?

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'98 F-150 XLT Reg. Cab Flareside 4x4, Black, 5.4l, 3.55LS, tow package, K&N, GTS headlight covers, Alpine changer w/FM mod, Clifford alarm system / Future considerations: 285/75/r16 Mud Terrain BFG's, bed cover, tonneau cover, suspension lift.