The most common question we get asked is what oil and additive to run in my differential. Here is what we would recommend.

Any differential that is running a posi-trac / limited slip with steel clutches we would highly recommend using GM AC Delco axle lube part number 89021672 and GM limited slip additive part number 992694.

Any differential that is running a posi-trac limited slip with carbon fiber or fiber clutches we would highly recommend using GM AC Delco axle lube part number 89021672 and Ford Friction Modifier part number CM485967

For Helical gear style posi-tracs that have no clutches we would suggest using a good quality Synthetic gear oil either 75/90 or 75/140 no additive required.

For open carriers in any differential you can use a good quality GL5 80/90 gear oil or a Synthetic oil.

If you are wondering if your posi-trac / limited slip has steel or fiber clutches here is a list of some common units:

• Ford OEM Trac-loc (fiber clutches)
• Dodge OEM Trac-loc (steel clutches)
• GM OEM Gov-lok (steel clutches)
• Auburn cone style posi (use GM oil GM additive)
• Eaton Posi (carbon fiber clutches)
• Dodge Trac-right ( helical style)
• Dana Spicer Power -Lock ( some came with steel some came with fiber)
• Dana Spicer Trac-lok (fiber clutches)