OK, so I now have a way to calculate 1st and 5th gear ratios if you already have the case open.
There will be 2 rows of gears. One row (gears A, B, and C) will be in line with the input and output shafts. The second row (X, Y, and Z)will be lower down in the case and slightly over towards the passenger side.
Please refer to the photo below which shows the inside of my T5. I showed a version of this photo to a tranny shop. He made calculations and told me what the gears were for 1st and 5th.
Follow this procedure:
X divided by A times B divided by Y = 1st gear ratio
which is 37 divided by 21 times 32 divided by 14 = 4.03 first gear
For 5th gear:
X divided by A times C divided by Z = 5th gear ratio
which is 37 divided by 21 times 25 divided by 51 = 0.86 fifth gear
