Rear diff oil change and friction modifier

So i've been reading and it seems some add the friction modifier and others don't. most agree that it is for limited slips that use clutch packs and our e-locker is a mechanical locking diff that uses and electronic solenoid. So when changing the rear diff oil is it necessary to use the friction modifier? any ford techs out there that can say once and for all yay or nay?

This is right out of a ford service manual. I do not think it will hurt anything if you use frition modifier. But it is not necessary.


Material Item Specification Fill Capacity
Additive Friction Modifier XL-3 (US); CXL-3 (Canada) EST-M2C118-A 118 ml (4 oz) to be installed before axle lubricant — Not to be used with Electronic Locking Differentials (ELD) Maximum Strength Retaining Compound
Loctite® 638™ — —
Motorcraft® High Contrast Hypoid Gear Marking Compound
XG-14 — —
Motorcraft® SAE 75W-140 Synthetic Rear Axle Lubricant
XY-75W140-QL (US); CXY-75W140-1L (Canada) WSL-M2C192-A and GL-5 2.84L (6.0 pt) — ELD only
2.60L (5.5 pt) — Non Traction-Lok equipped
2.48L (5.25 pt) — Traction-Lok equipped
Premium Long-Life Grease
XG-1-C or XG-1-K (US); CXG-1-C (Canada) ESA-M1C75-B —
Silicone Gasket and Sealant
TA-30 WSE-M4G323-A4 —
Threadlock and Sealer
TA-25 WSK-M2G351-A5 —

So i read this part

Not to be used with Electronic Locking Differentials (ELD)

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to mean we are not supposed to use it in the rear.

You are correct!

DirtNasty said:

So i read this part



to mean we are not supposed to use it in the rear.

Click to expand...

Not the first time 'nasty' has heard that....

SQAudiophile said:

Not the first time 'nasty' has heard that....

Click to expand...

Still sore?