Originally Posted by TS1955
I just put an Eaton posi in a rearend for a customer and one thing I can tell you is that the instruction said "DO NOT" use synthetic fluid. As far as the posi additive I'm not sure...sorry!
TS1955
Synthetic fluid is too slick and will cause the posi clutches to slip. They just won't lock up. I would reccomend an additive and there are several brands that will do. Dave