If it is a rebuilt transmission, I don't see the point as there shouldn't be any excess slip if the trans was rebuilt correctly. I do remember TripleEdge Performance transmission having a little Catepilar (I think it was) trans fluid mixed into the Dex for high Horsepower applications. I think the idea was that the thicker fluid would stick better to the clutch packs when they were spinning trying to hold Torque levels they weren't really designed for...