85% of the torque
but,
50% of the traction.
The big factor is the clutch, put enough weight on the rear, the 118% load on the clutch will cause slippage there before the axle fails.
The Colt had 3/4" axles and were known to fail, but, many are still operating. The Cub has 1" axles. I have seen no requests for axles in the want ads, other than fine splines for pullers.
I have been thinking about 27" tall rears on a custom Cub. High gear would only be for transport, not pullin'.