The gear ratios are slightly different between the ASU & CBB gearboxes,
also the ASU box has a cast iron transfer box & the CBB has a cast aluminium one.
Gear ratios are
—- ASU
CBB
1 — 3.77 to 1 — 3.77 to 1
2 — 2.21 to 1 — 2.21 to 1
3 — 1.34 to 1 — 1.36 to 1
4 — 0.97 to 1 — 0.96 to 1
5 — 0.79 to 1 — 0.76 to 1
F/D 3.68 to 1 — 3.64 to 1