I have written this up before....but TypeG is correct, it is the "GD". More specifically:

GD1 - 1.3/1.4 2 wheel drive (we get this as the GLi)
GD2 - 1.3/1.4 4 wheel drive
GD3 - 1.5 2 wheel drive (we get this as the VTi and VTi-S)
GD4 - 1.5 4 wheel drive.

Hope that is what you are after.

J