Tech Question, 2008 FX4

[enjr44]

2008 FX4 with the Torsen differential.

I am confused about changing the differential lubricant?? I know that the FX4 calls for XY-75W140-QL, WSL-M2C192-A, and SAE 75W-140 Synthetic Rear Axle Lubricant (which is different than the “other” 08 Rangers.

Now the confusion, this chart also calls for adding XL-3 friction modifier. https://www.fcsdchemicalsandlubricants.com/main/quickref/axlelube.pdf

But, I don’t understand why? A Torsen differential does not have clutch packs so why would you add a friction modifier??

OK, since I am here, the same chart and owner’s manual calls out XY-80W90-QL, WSP-M2C197-A, SAE 80W-90 Premium Rear Axle Lubricant for the front differential. Since there is a Torsen in the rear, is that still right?

Thank, Ed

 

[adsm08]

The Torsen unit does not require friction modifier, nor does it's presence in the rear diff affect the fluid spec for the front diff.

 

[gw33gp]

There is no call out for a friction modifier for the rear Torsen in my Ranger. I don't see a need for one either. It just specifies synthetic 75W-140. You should follow the book for the front differential. Although, I don't follow it exactly as I use 75W-90 because it is more readily available in synthetic than 80W-90.

When I had the Torsen installed in the front of my Ranger, I asked their engineer if I should use 75W-140 since that is what Ford specifies for the rear Torsen. He said I should still use what is specified by Ford for the front. He said using the lower viscosity gear lube would increase the torque bias a little for the Torsen but not significantly.