According to this site: https://workshop-manuals.com/skoda/octavia-mk2/power_transmission/gearbox_0am-dsg/technical_data/technical_data_for_the_gearbox/identification_characters_aggregate_assignment_ratios_(octavia_ii)/?fbclid=IwAR2y7M15Sx-Hgifjomnum7wkTwtAVlGqWxbqIPngI2gO1IP89sCQKqaBA60 
The 7 speed DSG gearbox has 3 different final drive ratios, one for gears 1-4, one for gears 5-7 and one for reverse? I have been trying to think why this would be the case? My only reasoning is that with a single final drive ratio that there wouldnt be enough space for some of the larger gear cogs?

My understanding of a DSG gearbox is that they are a preselect gearbox like the Daimlers used to have with twin layshafts, if you are in second gear the clutch for that layshaft is engaged and the other layshaft is free rotating, the brains will preselect either third or first gear on that shaft in anticipation (whether you are accelerating or decellerating) of the next gear change, the next change being effected by releasing the clutch on the 2nd gear layshaft whilst simultaneously engagin the one on the 1st/3rd gear one.

 

It sounds like each layshaft is driven at different speeds from the input shaft which would give different ratios to the numeric ones from the constant mesh gears rather than actually having different final drive (differential) ratios.

 

Cant wait to rebuild one one day, I have a penchant for gearboxes but have yet to get my hands on one.

7 minutes ago, J.R. said:

My understanding of a DSG gearbox is that they are a preselect gearbox like the Daimlers used to have with twin layshafts, if you are in second gear the clutch for that layshaft is engaged and the other layshaft is free rotating, the brains will preselect either third or first gear on that shaft in anticipation (whether you are accelerating or decellerating) of the next gear change, the next change being effected by releasing the clutch on the 2nd gear layshaft whilst simultaneously engagin the one on the 1st/3rd gear one.

 

It sounds like each layshaft is driven at different speeds from the input shaft which would give different ratios to the numeric ones from the constant mesh gears rather than actually having different final drive (differential) ratios.

 

Cant wait to rebuild one one day, I have a penchant for gearboxes but have yet to get my hands on one.

 

I understand the idea of the odd gears being on one shaft and the evens on the other with each using its own clutch, but that page I linked to specifically says the lower 4 gears are on one final ratio while the top 3 gears are on another. It also says reverse is on yet another final ratio? 
You are likely right in that there is only one final gear on the axle, how could there be 3? Unless where its front wheel drive they get slid into place by the car automatically? Or could the gears be laid out so 1-4 are on one shaft and 5-7 on the other? There are only 2 clutches though so that wouldnt make sense especially once you add in reverse.

I suspect that its incorrect use of terminology or perhaps the English use of final drive ratio always referring to the differential is not the same in other languages, also could be a translation error.

 

I think they are talking about the compound gear ratio from the engine crankshaft to the gearbox output shaft, on a normal gearbox all forward gears will only have one gear pair to calculate the ratio although reverse will have two.