Differential fluid change - do I need friction modifier?

[Wilson]

It's all good and you can use up to 30% ethanol

 

[Ruger]

It's all good and you can use up to 30% ethanol

This reminds me of a joke my daughter told me....

A pirate walks into a bar, see? He's got a patch over one eye, a peg leg, a hook instead of a hand, and a Raptor steering wheel pierced through his *******.

The bartender asks him how he lost his eye, and the pirate says, "Arrr, lost it when assaulting a merchantman."

The bartender asks how he lost his hand, and the pirate says, "Arrr, stealing from the Cap'ain."

Next the bartender asks him how he lost his leg, and the pirate says, "Arrr, cannon ball."

And the bartender asks him about the steering wheel, and the pirate says, "Arrrr, it drives me nuts."

Thanks for reminding me of a really terrible joke, Wilson!

 

[Ruger]

All right, back to the dilemma. The current 2014 manual specifies 75W-85 and does not mention friction modifier, and the manuals that came with my 2011 specify 75W-140 and 4 ounces of friction modifier. Are we talking about the SAME DIFFERENIAL on the 2014 and 2011 models, or have they made some internal changes that require a different gear oil? How is an owner to know what lube to use???

 

[Wilson]

It probably depends on what type of deal they get when pre ordering

 

[Vash]

Maybe this helps...or confuses the subject even more?

From the 2010 Ford Workshop Manual...Sorry I'm not paying for the latest version, but the engine and driveline service info should be the same:

• Friction Modifier: XL-3 (US); CXL-3 (Canada) EST-M2C118-A
• Motorcraft® SAE 75W-140 Synthetic Rear Axle Lubricant: XY-75W140-QL (US); CXY-75W140-1L (Canada) WSL-M2C192-A and GL-5
• Silicone Gasket and Sealant: TA-30 WSE-M4G323-A4

Removal (referring to the rear diff cover)

With the vehicle in NEUTRAL, position it on a hoist. For additional information, refer to Section 100-02 .
Remove the differential housing cover.
Remove the 12 differential housing cover bolts, and drain the lubricant from the axle housing.
Remove the differential housing cover.

Installation

NOTE: Remove all of the silicone gasket and make sure the surfaces are free of oil before applying the new silicone gasket.

Clean the gasket mating surface of the axle and the differential housing cover.
Apply a new, continuous bead of sealant to the differential housing cover as shown.

NOTE: The differential housing cover must be installed within 15 minutes of application of the silicone, or new sealant must be applied. If possible, allow one hour before filling with lubricant to make sure the silicone sealant has correctly cured.

Install the differential housing cover and the 12 differential housing cover bolts.
Tighten to 45 Nm (33 lb-ft).

Remove the fill plug.
[highlight]NOTE: For non SVT Traction-Lok® axles, first fill the axle with 118 ml (4 oz) of friction modifier. No friction modifier is used on SVT axles.[/highlight]

Fill the axle with the specified amount of axle lubricant and install the fill plug.
Tighten to 30 Nm (22 lb-ft).

Now, if someone with access to OASIS and/or the latest Workshop Manual can confirm this hasn't changed. Anyway, I'm going to be doing this service soon and I DO NOT plan to add friction modifier. If I hear any chatter or anything unexpected then I'll add some, but I don't anticipate needing to do so with a quality synthetic lube. I have a case of Amsoil ready to go into the front and rear diff in the appropriate viscosities.

Full disclosure...I am NOT a mechanic. I'm just sharing what I've found. Take it or leave it. I'm just an IT guy that holds a wrench occasionally.

My personal take is still that, unless your rear is special and has clutch plates in it like an LSD, then you don't need friction modifier.

 

[Madcowranch]

From Amsoil's website: AMSOIL Severe Gear is compatible with most limited-slip
differentials.

So I 'm assuming it already has a FM added Vash.

 

[Vash]

Interesting note from the online listing for Amsoil's Slip Lock Additive (friction modifier):

NOTE: AMSOIL Synthetic Gear Lubes do not require the use of this additive. However, not all differentials respond the same and if chatter is noticed, the addition of AMSOIL Slip Lock will eliminate it. For chattering differentials not running AMSOIL Gear Lube, this product is an excellent solution to the problem.

You may be right, Rich. Regardless, I think this is a case where you don't need to go out and buy a separate 4oz additive unless you notice chatter from the rearend. Basically, friction modifier doesn't hurt if you add it unnecessarily, but it can help if you notice chatter. Clear as mud. Anyway, I don't plan on adding anything particularly since I'm going with Amsoil Severe Gear.

 

[Ruger]

Vash,

EXCELLENT information, and I am quite inclined to agree with you that friction modifier is probably not needed in the Raptor rear end. What is "chatter?" What are the symptoms of chatter?

Unfortunately this does not clear up the question of the recommended weight of the gear oil. Earlier manuals specify 75W-140 and later manuals specify 75W-85.

 

[Vash]

This is from the Amsoil Slip Lock Additive site, but good general description of chatter:

Limited-slip (or positraction) and locking differentials are traction-increasing devices. Locking differentials transfer all available torque to both wheels. The teeth of the spider assembly engage with those on the locker clutch, causing both axle shafts to operate as one. Locking differentials don't allow one drive wheel to spin while the other remains stationary. Instead, they keep both wheels in drive mode, but unlock to permit different wheel speeds when turning. The engaging and disengaging of the teeth on automatic locking differentials often causes a banging and clunking sound. Manual locking differentials usually use an electric motor or vacuum diaphragm to engage the locker, reducing this noise.

Limited-slip differentials allow different wheel speeds when turning, but when one wheel loses traction, greater torque is transferred to the wheel offering more resistance. Limited-slip differentials make use of friction between clutch plates, as opposed to the meshing teeth employed by locking differentials. Transferring less torque per side, limited-slip differentials are generally smoother and quieter than locking differentials, but still sometimes "chatter" when transferring torque to the wheel with traction.

Basically, chatter is noise/vibration experienced when locking or LS diffs engage to transfer torque to both wheels.

 

[Yukon Joe]

Had the rear diff oil changed at the dealer a few weeks back. (I know, bad idea please don't judge me... lol). They did NOT remove the rear cover. They opened the fill plug and pumped out the old fluid and the refilled with the supplied Amsoil.

Yesterday, I changed the rear diff cover to the aFe aluminum cover and added new Amsoil fluid. The auf that was in there for a few weeks didn't look too bad, but didn't want to put it back in. Write up to come on cover install. I did not add any friction modifier.

Yukon Joe
www.RUNRAPTORRUN.com