i have a 2006 fx4. and im about it change the rear differential fluid. i want to know if i have a a limited slip differential.

 

Will it scratch out both rear wheels at the same time? Has it ever made a shuddering noise when turning a tight circle? With both rear wheels off the ground and turning one, will the other one turn in the same direction? Those are all attributes of a limited slip diff.

 

there should be a tag on one of the pan cover bolts.......... there should also be a code on the door sticker-- drivers door column.

 

FX4 '04-'08 all have limted-slip rear diffs. Your axle code should be B6 on the door jamb sticker.

 

So, bottom line, if you have one, be sure to use the special lubricant plus the Ford additive for quiet, trouble-free operation.

 

My 08 shutters when I take off and turn at the same time. What is the exact name of the additive? Would like to see if that helps

 

Genuine Ford Fluid XL-3 Friction Modifier Additive - 4 oz.

 

You can buy a 7 oz tube of friction modifier at Auto Zone. That's what I have used for years. Cost about $8.