PJ, just noticed your post in the Matrix thread. The diff oil set up is a bit of a tough one for the Fun Factor. It kind of depends on which engine you are planning on using in the truck. If you will be using a small block, I would go for a set up similar to a 1:8 buggy. Something like 5k front, 7k centre and 1k rear. If you will be using the .28 then a truggy set up may be more appropriate. Say 10k front 30k centre and 5k rear. The centre diff weight is to prevent the front wheels unloading and ballooning the tyres as the weight goes on the rear tyres inder acceleration. Obviously the bigger the engine, the greater the likelyhood of the front wheels picking up. Hope that made some sense.