Originally posted by eX.A.K.R.:
As [b]Volvo Olympian said above, the gearbox sound. Voith
gearboxes have a distinctive whistling sound, making buses sound
rather futuristic; perk your ears up for them when the bus
decelerates - it will go something like
"wEEEEEeeeeeeeeuuu...".
As for ZF, I'm not too sure, but I heard some of them have a
howling sound.[/b]
as long as the retarder is LOUD it should be a voith, if not its
should be a ZF 
and for a Voith, it shift its gear slower than a ZF
