Pressurized ATF acts around the movable 50 % of the pulley, transforming its diameter. “For that reason,” said Maldonado, “a CVT transmission constantly adjustments gear ratios as the two movable pulley halves slide over a shaft, when the opposite 50 percent with the pulley continues to be locked set up.” https://gearboxcvt17383.thelateblog.com/34669331/gearbox-cvt-options