Open Differential Torque Leakage

There are incorrect views about open differentials in the Internet. To this point specifically, an open differential provides exactly a 50/50 torque split between each axle at all times, by design.

Open Differential – Cut Away View

The differential’s role is to allow each wheel to travel at different speeds, but the torque split across the axle ends is always equal.

You can Google that “torque split open differential” and there are lots of articles describing the mathematics and engineering behind this fact. Here is just one, for example.

If a driven wheel loses traction there is no “torque leakage” out of the free-wheel. In fact the engine torque delivered (or load) drops immediately to zero. This is why the engine will rev-up (become unloaded) when a wheel(s) loses traction.

You can test how much torque a free-wheel can absorb in your garage by lifting a front wheel (in 2WD) and using a torque wrench to loosen the wheel nuts. Measure how much torque you can achieve. A free-wheel cannot absorb torque.

Traction Control systems and clutch based LSDs use this differential equal torque split across the axle to provide traction, by adding torque to the free-wheel axle. This allows the engine to deliver torque to the free-wheel axle and, by design, exactly the same amount of torque to the other axle (with the wheel with traction) allowing the vehicle to proceed.

There are only two cases, I’m aware of, where the 50/50 split across the differential axles is not designed in. One in the centre differential of various Mercedes Benz AWD systems, where the axle pinions are built with different numbers of teeth to provide torque bias to the rear (e.g. 60/40). The other is in Torsen differentials (such as Quaife, Peloquin, Eaton Truetrac brands) which use worm drive mechanics to multiply the torque across the differential center.

Anyway, I just wanted to share that since the “torque-leakage” myth pops up all over the place and it is best to put an end to it.

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