B3 1.6TD vs B4 1.9TDI gear ratios

[trev]

I have a 1.9D (1Y non-turbo) engine in my B4 Passat with the gearbox from a 1.6TD B3 Passat, SB engine code. I have been offered the gearbox from a 1.9TDI (AAZ) basically for free. I would swap it into my car if I thought the ratios meant better fuel economy.

I see reports of AAZ or 1Z powered B4s getting close to 80MPG whereas my 1.9 non-turbo gets an average of 44MPG with a one-time record of 49MPG. I wonder if it's the engine or the gearbox that contributes towards the phenomenal fuel economy of the TDI B4s?

Does anyone have a chart of the gear ratios in the B3/B4 transmissions? Any advice appreciated