@TechConnectify on patents: for GM specifically, I don’t think this was an issue at all. GM was making two-mode power-split transmissions as early as 2003 (the Allison EP40/EP50, now known as the H40EP and H50EP), and selling consumer vehicles with them in 2008 (the 2ML70 used in the GMT hybrids, as well as the BMW, Chrysler, and Mercedes vehicles using that powertrain). and, the Gen 2 Volt basically used a scaled down version of the Allison EP system. for other automakers, maybe? but, yeah the patents are dead now. and, finally, for locomotives… as I understand the problem there isn’t torque output per se - gearing turns horsepower into torque - but rather making the kind of gearbox that has wide enough range to get a 2 mile long consist moving from a stop uphill, as well as to go 80 MPH, while surviving behind a 3-4000 hp diesel. diesel-hydraulic systems using torque converter automatics are a thing in DMUs that have multiple smaller engines, but not so much in locomotives. (also, with longitudinal engines, you’d have to turn the power 90 degrees and eat some losses there. and, with a diesel-electric, you get dynamic braking for free as an additional way to slow the locomotive down.)