https://vtol.org/store/product/load-sharing-test-of-the-ch53k-split-torque-main-gearbox-2474.cfm Load Sharing Test of the CH-53K Split Torque Main Gearbox] AHS International/Sikorsky, 2009 The gearbox assembly including rotor hub and rotating control system weighs around 11650 pounds , Gmirya, Y., Alulis, M., Palcic, P., Leigh, L. "Design and Development of a Modern Transmission: Baseline Configuration of the CH-53K Drive System ", NASA, 2011.