Does anyone know the gear ratios of the centre distribution differential and the rear differential of the Audi V8 automatic (3.6l & 4.2l)(rear differential also in 100quattro & 200quattro) ??

Don't have them for the V8, but here are the 100 and 200 ratios:

200 Automatic:
1st: 2.71:1
2nd: 1.50:1
3rd: 1.00:1
Reverse: 2.43:1
Final Drive: 3.08:1

200 Manual:
1st: 3.60:1
2nd: 2.13:1
3rd: 1.36:1
4th: 0.97:1
5th: 0.73:1
Reverse: 3.50:1
Final Drive: 3.89:1

100 ('92-'94) Automatic:
1st: 2.71:1
2nd: 1.55:1
3rd: 1.00:1
4th: 0.68:1
Reverse: 2.11:1
Final Drive: 4.00:1

100 ('92-'94) Manual:
1st: 3.50:1
2nd: 1.84:1
3rd: 1.30:1
4th: 1.03:1
5th: 0.84:1
Reverse: 3.44:1
Final Drive: 3.70:1