Friction modifier for differentials?

[saburai]

I noticed in another thread, but that the poster said he was running a additional friction modifier in the diffs. Could someone please enlighten me on is? Is this a factory requirement? Thanks all!

 

[u2slow]

I skip the modifier on well-used posi diffs. Usually get some grip back.

You shouldn't ever need more additive than the factory spec, but if you overfill, and/or have a fresh new unit, perhaps more is preferable to avoid chatter and nuisance tire scrubbing.

 

[Booyah45828]

Some oe's require it. Some fluids say that they come with it already in them. We use valvoline which is one that supposedly already has it. But we keep a few tubes on the shelf in case we service one and it chatters afterwards. NAPA # SL2411 is the stuff we use.

 

[Therkhan7_3Turbo]

I put fresh oil, drive and then add 1 oz at a time till it stops chattering. This is on older well used Differentials, newer well maintained trucks/Diffs I usually just go straight for whatever OE recommends.

 

[saburai]

So the question is, is it required for my '94 f250 4x4 idit? I'm at a friends shop, we've got it on a lift draining, so it's a time sensitive question...

 

[u2slow]

If it was me, skip it. If it's acting funny, add it later.

 

[saburai]

If it was me, skip it. If it's acting funny, add it later.

Thanks for the quick reply!
Is the friction modifier for limited slip diffs only? Little more than 150,000 on the truck, if that effects your answer.

 

[u2slow]

Correct, no modifier is spec'ed for open diffs.

 

[saburai]

Axel code is C5, LS or open?
Would there be a problem with putting friction modifier in a open duff?

 

[u2slow]

IIRC, axle codes with a letter are LSD. Modifier doesn't hurt, or help anything, in an open diff.

 

[saburai]

Thanks! The Chillman looked it up for me. C5= 4.10 LS so it's getting a shot of friction modifier. Thanks for the help Gents!