To be more specific, the new B9TLs Voith gearbox model is the
VOITH D864.3, 4-speed gearbox, and is currently the only bus to be
eqipped with 4-speed Voith gearbox, other Voiths were all 3-speed.
ZFs has alot of speeds available here. There were 4 speeds(ZF
4HP500/502 most common one), 5-speed(ZF 5HP590: used in the Scania
L94UB,SBS9888Y), 6-speed (ZF 6HP502 : used in the B9TLs)