In message m, Martin
Underwood writes

I thought car auto transmission used epicyclic gears ie a mechanical
connection between engine and prop shafts, though via a hydraulic
clutch rather than a true hydraulic transmission in locomotive where
the engine drives a hydraulic pump which sends high pressure oil to
turbines attached to wheels - ie with no mechnical connection between
engine and wheels.
If you look at the Voith transmissions, some stages are converter and
some are fluid flywheel. Very similar apart from torque multiplication
in the first and not in the second.
--
Clive