Ball VS Gear Differentials
Many people struggle with what type of differential to use in their off road cars. Here is a quick rundown of how we determine what will provide us the most performance at the track.
One key property that makes ball differentials and gear differentials react differently is how they bind up under loads. I’m not talking about the transmission binding up and slowing down how fast you can accelerate, but rather how resistant they are to changes in speed between the left and right tire. On the bench, they can seem similar. Spin one tire forward and the other spins in reverse. This is under no load, so it doesn’t accurately portray what happens when you are accelerating.
For 2wd vehicles on a low traction or rough surface, you want your car to be as stable as possible when you accelerate to avoid spinning out. Ball differentials don’t bind up as much when they are placed under load, so they can more efficiently react to changes in traction. If one side loses traction, the differential is more effective at keeping the car going in a straight line. Or if you are accelerating out of a corner, it more readily unloads excess torque to the inside tire, preventing the outer tire from breaking traction.
As traction increases and the surface gets smoother (or you are running a 4wd vehicle), usually you will run faster laps with more on power steering. A gear diff acts more like a limited slip differential when you accelerate as it wants to keep the left and right tires rotating at the same speed more so than a ball differential. This puts relatively more torque to the outside tire than a ball diff would, helping the car rotate as you accelerate away from the corner. This effect can be adjusted by changing the viscosity of the oil inside the differential.
The examples above are for properly built and maintained differentials. If you aren’t sure how to set up a ball diff or simply don’t have the time to do regular maintenance, we suggest a gear diff no matter what conditions you race on. A gear diff with the correct viscosity oil will serve you better than a crunchy ball diff. Now go tame your terrain!
