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Redcat Racing How to Series: Tuning Diffs

A differential allows one wheel to spin faster than the other. Many RTR vehicles come with loose diffs that have grease in them. Most diffs that I’ve come across are sealed well enough to hold silicone diff oil. This allows you to tune the way the vehicle handles. If your differential will not hold diff oil, you can seal it with some silicone sealant. Apply a VERY thin bead along the edge of the diff casing where it will join to the main diff gear. You’ve essentially just created an O-ring or rubber seal. There is usually a gasket here, only use silicone if the gasket is missing or damaged.

Now fill up the differential with silicone differential oil. The thicker the oil, the more the diff acts as a posi-traction, sending equal power to each wheel.

Here’s a tip on diff oil weights. I usually use a heavier weight oil in the front than in the rear. Keeping the rear light allows the vehicle to turn easier. Putting a heavy oil in the rear has the opposite effect, making the vehicle more difficult to turn on high traction surfaces.

The heavy weight oil in the front helps to pull the vehicle through the turn. Having a light weight oil in the front usually results in the inside tire ballooning while taking a turn.
If your vehicle has a center differential, like the Hurricane and Monsoon, start with a medium to medium heavy oil. The center diff does a great job of keeping the vehicle under control while accelerating. Using too light an oil will rob too much power from the rear tires and using a diff lock will make it too easy to pull wheelies, unless that’s your thing, wheelie king.

Lets recap.  A good starting point would be, stiff front diff. A medium center diff. & a loose-medium rear diff.

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