HI,
My rear allignment was off a hair and it would cause a creek under load, I losened the rear clamp and pressed hard on the brakes and then while holding the brakes I tightned the rear clamp , All I know is it stopped, my guess the slight allignment was enough to cause the crank to creak.
Doug
PSPS Scotch will make it less of a concern and is good for your health due to scotch vitamins..its made from grains right...