Found it! From about 2 months ago. I made some changes some things just weren't to clear.
ORIGINAL: Little Stampy
Front- thicker gives you less steering responce off throttle and better on throttle "posi" traction pull out of corners because of the even power to both wheels and lighter oil gives lots of off throttle steering responce but less front wheel bite out of the corners because the power gets thrown to the wheel with the least traction.
Center- thicker gives more 4wd which can give you some under steer because the rear is pushing the front tires a long to much but great drive with all 4 wheels accelerating the buggy hard and thinner oil will give you a lot of power to the front wheels so it pulls the buggy around on the throttle more giving you good on throttle steering but lacks a little acceleration because mainly the front tires are pulling instead of all 4 digging.
Rear- thicker will give you understeer off the throttle because of the resistance between each wheel spining to the other but as long as your on the throttle and have the tires broken loose of traction it will of corse bring the rear of the buggy around but you can't always break the tires loose like that which can make handling inconsistant... thinner oil will give you quick steering because of the low resistance that will let each wheel spin however fast they need to and it will give you a hard time to break both tires loose because all of the power goes to the tire with the least traction which is the inside tire. thinner rear oil tends to make the buggy feel like the rear is just swinging in the wind especially if you have something like the MP777 SP1 which has a whole lot of steering already but in something like a hyper 7 which normally has understeer it works pretty well in it unless you like that understeer.
Thats basically it for diff oils... I really don't know how much you knew about how the diffs worked in the first place but hopefully this will help you or anyone else looking on the thread.
Oh yeah and some things on rear toe in. More rear toe in will give you more straight ahead stability and make it harder to break the rear loose of traction but when you do break the rear end loose its going to break loose harder and its going to snap back when you regain traction... its really not good for flat tracking.
Less rear toe in will give you less straight ahead stability and less rear traction. It will make it easier for the rear end to break loose but it will be a lot smoother and easier to control when you are in a slide.