[OTreborO]

I read somehwere about possibly having to add some kind of Ford miracle stuff if my rear gear oil if my differentional was a certain kind to help reduce friction???

How do I determine if I need this wonder drug

[99mustang232]

friction modifier is used for the protection of the clutches in limited-slip differentials, there are also aftermarket companies that make this stuff too, like redline.

[BULLITT]

If its the first time filling up the posi. Like if it was never used add the 4 oz bottle. If your just putting new gears in or changing the fluid allyouneed is like 2 oz half the bottle. They say like my 03 cobra posi unit. I only need it on the initial fill. After that i dont needot add it anymore. If im just changing the gear fluid.


And its not really to stop friction to much. Its to help unlock the posi clutches so you can make turns whithout hearing the tires chirp. thats all.

I dont add any on just chaging fluid. To much if itand sooner or later ull get one wheel peels when it gets hot in their.

[Twist 2 Go]

yes too much will cause issues but it has to be A LOT. Synthetic fluid is also more forgiving when it comes to lack of modifier and some fluid has the modifier already added. I always add 1-2 bottles everytime I remove a rear cover. Not like Ford doesn't have a problem here lately with binding diff clutches.

[OTreborO]

Is there a way to tell which rear I have. I didn't think I saw any cluthes when I took the gasket off and changed the hypoid oil.

[Twist 2 Go]

if there was a small metal tag under one of the cover bolts, look on it and you'll see a # that says 2L73 or 3L08. If the L is present it's a limited slip. If there is just a blank space where the L is in the example above, it's an open diff.

[mdvaldosta]

If you've got a 4cyl car then it comes stock with a 7.5" open differential. All the 5.0's from 86 up (maybe 85 I can't remember) whether LX or GT came with an 8.8 trac loc.

[vfast]

if you use redline gear oil it has it in it already