Friction modifier needed for a 9”

[Gas Pig]

I have a rebuilt Ford 9” and Dana 44 both with factory posi. How much addictive friction modifier (Motorcraft) do I need for each axle?

Thanks Jeff

 

[.94 OR]

If you are buying the bottle from Ford, I believe it takes the full bottle. I think mine are about 4 oz size.

 

[bmc69]

I always just run the HP gear oil that already has the friction modifier in it. Valvoline or Red Line.

 

[Speedrdr]

I never had to change out or add to the front differential in all the years I owned my 72EB so I’m no help there. However, having had to replace rear axles multiples of times I was conversant with fluid in the rear 9”. Added 1 pint of ford friction modifier each time fluid was changed out. Not saying this is spec for the chunk, but it worked.

Randy

 

[DirtDonk]

I think the general use expectation is one bottle per clutch type differential.
Isn’t supposed to matter what brand (Ford, Dana, GM…) or type of differential (as long as it’s a clutch limited-slip), you just use one bottle.

Having said that, I had a Ford Racing four-spider 9 inch track lock that required two bottles.
I was using Stay-Lube brand non-synthetic gear oil that was supposed to have the additive already in.
Still needed the friction modifier to keep it from growling.

Very possible that it was the clutch material and extra preload from the springs of the performance version, but I did give it a couple of months to soak into the clutches, just in case. And it still needed the additive.
Fast forward to the next oil change, and I used Redline synthetic, and it did not require any additive.
It was also so slippery that the differential did not transfer as much torque to the loose wheel as it did before with the regular oil.
Noticeably more slippage.

 

[Gas Pig]

If you are buying the bottle from Ford, I believe it takes the full bottle. I think mine are about 4 oz size.

Yes my Motorcraft bottle is 4 oz. I couldn’t remember if it was one or two full bottles per axle.

 

[Gas Pig]

I think the general use expectation is one bottle per clutch type differential.
Isn’t supposed to matter what brand (Ford, Dana, GM…) or type of differential (as long as it’s a clutch limited-slip), you just use one bottle.

Having said that, I had a Ford Racing four-spider 9 inch track lock that required two bottles.
I was using Stay-Lube brand non-synthetic gear oil that was supposed to have the additive already in.
Still needed the friction modifier to keep it from growling.

Very possible that it was the clutch material and extra preload from the springs of the performance version, but I did give it a couple of months to soak into the clutches, just in case. And it still needed the additive.
Fast forward to the next oil change, and I used Redline synthetic, and it did not require any additive.
It was also so slippery that the differential did not transfer as much torque to the loose wheel as it did before with the regular oil.
Noticeably more slippage.

So I’ll just add the 4 oz bottle per axle and call it good!

Thanks for everyone chiming in!

 

[Broncobowsher]

Read the bottle of gear oil you are using. Many times it already has the modifier built in. If so, no need to add. But if it doesn't state, you need to add.

 

[DirtDonk]

Oh, and if you don’t already know this…
Don’t get it on your clothes!
And wear gloves!
And wear a mask of any kind that seals well!

All of this to keep what is probably the nastiest smelling stuff you’ve ever had the misfortune of experiencing, from sticking to the back of your throat once you breathe it in.
And to keep you from being kicked out of the house if you get it on your clothes.

And no, I am not kidding in the slightest.

 

[Speedrdr]

DD, the only level of stench that I can relate it to (as an RN) is a gastrointestinal bleed. Once blood has passed through the body, it will make you gag and the smell stays in your nose for days!
Friction modifier is WORSE.

Randy

 

[Gas Pig]

Only one other time I had to use the modifier and yes the stuff stinks like no other! I have heard some guys call it “sunk oil” … actually that’s not to far off of a description, a nasty smell that won’t go away!