[timstith]

Dana M 300 rear differential. 2019 F350 DRW 6.7…. Question, I’m trying to determine if I need to add friction modifier to the oil when I change the rear diff fluid… I do not have the electronic locking differential, and without limited slip. Do I add the friction modifier? If so how much? Any help would be appreciated… TIA.

 

[bugman]

Without limited slip you shouldn't need any friction modifier for it.

Most synthetic gear lubes now days already have it in their formula and they have a rating of GL4 or better.

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