RCU Forums - Dif oil

I have kept these two Diff documents on my computer for just this case,....i hope this helps.

" I look at it this way:
1st remember and this is all you have to remember is that a diff's job is to transfer torque to the side of the diff with the least amount of traction, i.e. least amount of weight transferred, i.e. least amount of traction (This is opposite a torsen by the way).

Center diff fluid:
Say you accelerate, weight transfers towards the rear (your buggy squats - how much depending on several factors such as rear antisquat plate, how hard you are on the gas, etc), a center diff with very light oil will "diff" more towards the front to try to balance the load and stabilize the buggy. This is great on a slick or maybe a tight track where you want to feel the front diff pulling your car a little more and keep you from "spinning out."

Now, say you put in very thick center diff oil in your center diff.
You accelerate, weight transfers towards the rear, a center diff with very thick oil will "diff" less towards the front but will give you the most torque at the rear of the buggy, i.e. more acceleration. This is great for high bite tracks but on a slick track you may find your rear end swinging around more.

BUT, straight line acceleration is but one aspect of a center diffs purpose. Say you are on a track and you approach a whoop section. A car with very light fluid will transfer more torque to the front of the buggy as soon as the front tires begin to loose contact with the apex of the whoop, hence your rear end feels less power and consequently the front of your buggy's nose comes down nice and fast ready for the next whoop. Your center diff is constantly "diffing" to keep the car balanced through the whoops. Now, if you had very thick oil in the center, the nose of the buggy would come down a little slower because it will not diff towards the front so fast. This can cause your buggy to get out of shape easily because your front tires are not in contact
(Think steering) as much with the ground.

Also, center diff oil can even depend on what engine you are running. if you have an OD MOD, and you go too light on the center oil, you will find your front tires ballooning to the point of almost flying off the wheels down the straight away, so you may increase the center oil weight a bit.

Ok, now for my 2 cents on front diff fluid. This will control torque transfer from the left to front tire and vice versa.
Let's say you have very thick front center fluid and you exit a left hand 180 on the gas. Your right front tire has the most traction and hence, if you want the tightest steering, you would want most of the torque to stay on that outside tire, and hence you would use heavier front diff fluid. However, if you want more turn-in (which happens at the very beginning of the turn up until the point where your car has transferred more weight to the outside tire), you could use lighter front diff fluid.

BUT, the front diff is not just there for turning. Let's say you hit a bump with only the left front tire of your car. With light front diff fluid, more torque will transfer to the tire with the least amount of traction than with thicker oil, i.e. the right tire starting to come off the ground due to the chassis lifting, hence the front will stabilize itself more than a car with thicker front diff fluid.

The rear diff follows the same principle of the front diff.

I know this was long and boring and winded, but I just wanted to get my feelings out there as an alternative point of view. I am also an RC photography fan and I love watching and photographing diff action on buggies. So I am always noticing how many different buggies including mine are diffing by watching and photographing their tires at different times.

What I said above is not the be-all end-all gospel but just my experience.

Oh yeah, the front diff thing is also a reason you find some buggies
(At least mine) will have more front steering with a front sway bar on some of the faster corners. The bar keeps the car from transferring too much weight to the outside tire, thus reducing the front diff action.

#2 ..........

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.

These two documents help keep myself in check when i'm getting ready to try something stupid with my diff's. :eek:

JEFFRO503