Hi Padders, I think you are misunderstanding their text. Speaking specifically about the 8HP45, there are gen 1 and gen 2 boxes of the 8HP45. There are a few key differences to be able to tell them apart but effectively the gen2 is just an updated version of the same box. One key difference is the gen 1 had a A.S.S shutdown time lag of 1.5 seconds whereas the gen 2 is immediate. The 8HP50 seems to be a run of something new as it has different gear ratios, unlike the other 8HP line gearboxes which have the same gear ratios regardless of model number, ie: 8HPX where X relates to the capable torque input.
So, the 8HP50 is not the second generation of 8HP45's. I can see on documentation relating to my car that the gear ratios do not match that of the 8HP50 but they do match the 8HP45 (and others from this link in the technical information tab:
http://www.zf.com/corporate/en_de/pr....shtml#tabs1-1).
I cannot find any technical information at all about the 8HP50. It's not listed in the link above.
I also read somewhere that the 8HP line is the 2nd generation of ZF 8 speed gearboxes, with reduced internal friction giving better fuel economy. In fact I believe it is mentioned in the ZF promo videos on their website.