Shear Modulus Calculator
Stiffness against sliding deformation, from a shear test's numbers.
Stress over strain, sideways
S = (F/A) / (x/y)
Push the top of a block sideways while the bottom is held: stress is force per area, strain is slide per height, and their ratio is the shear modulus. Steel sits around 79 GPa, aluminium 26 GPa, rubber a few hundred kPa, which is why rubber pads isolate vibration and steel drive shafts don't twist much.