[kidcongo]

as long as it is silicone grease on the balls I think your are OK. I have used Kyosho clear silicone grease and tamiya silicone, and cant say I notice a difference. The reason it is silicone grease is that silicone grease has very low "shear strength". This means that the grease will squeeze out of the way and allow direct contact between the diff balls and the pressure plate, causing the balls to "roll" so the diff does not slip. At the same time the grease lubricates the surfaces where the balls roll inside the plastic cage of the nylon diff gear where the pressure is not a great, preventing wear of the nylon part.

For the diff's small 'thrust' bearing you are only interested in having minimal friction so they use AW or Black grease, which is a grease containing molybdenum or aluminum particles that has a very high shear strength. In other words it doesn't smear out of the way under pressure. Moly type "black" grease is what you see in high pressure applications like a tractor-trailer 5th wheel plate.

In your ball diff, you never want the balls to slip, you want them to roll along the plate. If you use normal grease, black grease, or ceramic grease that is not for diff plates, you essentially make everything way too slippery, and the diff balls will not function like the planetary gears they mimic in a standard gear diff. They will slide along the plate, which puts flat spots on them and makes the diff feel "gritty" before it's time.

If you look at the steel balls from the "gritty" diff they are typically covered with a multitude of microscopic flat spots.