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Frequently Asked Questions: Eaton Posi

Find answers to common questions about the Eaton Posi differential here. 

What kind of oil should I use in my Posi? Can I use synthetic oil? Do I need friction additive/modifier?

  • A quality, petroleum-mineral based, GL5 rated 80w-90 gear oil should be used.
  • It is necessary to add a four-ounce bottle of friction modifier for optimum performance (if friction modifier has not already been added to the petroleum-mineral based gear oil that the customer selects).
  • While some customers have found that synthetic oil works well in this application, Eaton has not confirmed under test conditions that all synthetic oils (with added friction modifier) are compatible with Eaton Posi applications.

Is the Eaton Posi rebuildable?

Yes, there are three main types of service kits available to rebuild your Posi differential: internal spider and axle gear kits, clutch kits, and preload spring and plate kits. 

What is the warranty on my Eaton Performance differential?

Eaton Performance differentials (including Eaton ELockerEaton ELocker4Eaton PosiDetroit Truetrac, and Detroit Locker) are warranted for one year against manufacturer defects. Download the full warranty document.


Can I upgrade my Eaton Posi?

Yes, both the clutch disks and the preload springs can be altered for extreme off road and drag racing applications.

Eaton Posi units come equipped with 400lbs of preload. They can be increased to 800lbs, or even decreased to 300lbs or 200lbs to tune the handling characteristics of the differential to your vehicle. There are several types of clutch service kits in varying friction material style and number of plates. Reference our application guide, or contact the Eaton Performance customer service team for details, part numbers, and availability.