SAE J 3249:2026-07-14

This recommended practice describes the procedure to measure and report the operating efficiency for all types of constant velocity joints (including fixed and plunging/end motion type joints) used in cars, SUVs, and trucks. This includes halfshaft as well as propshaft applications. This does not apply to non-CV joints. Rotational inertia is not considered within the scope of this recommended practice. This recommended practice provides a common method to quantify and report the operating efficiency characteristics of a CVJ. This practice does not apply to parasitic losses (spin loss, churning loss, or zero torque loss) as experienced on deactivated AWD/4WD systems. The losses in this condition are significantly less and require higher accuracy than what is required in this recommended practice.