It's a different concept. Read up on the differential
wandler concept that Voith's DIWA range uses. It's very
different to a conventional torque converter design.
Also, because of the wider spacing of gear ratios, it is not
possible for a Voith gearbox to shift at the same engine speeds as
a ZF-EcoLife without labouring the engine.
to answer the OP, the Voith DIWA Concept merges the torque
converter with the retarder into a single unit, hence DIWA (DI
-> Differential, that is torque converter; WA -> Wandler,
that is retarder). simply put, the Voith torque converter functions
BOTH as a torque converter and retarder under startoff and braking
respectively, and this design philosophy/implementation underpins
the vast difference in acceleration and braking characteristics
between the ZF and Voith transmissions.
could PoweredByCNG explicitly justify the above claim with the
specific gear ratios?