What is legal rate on judgment that has replaced a defaulted loan?

The question as posed is impossible to answer. Different jurisdictions can impose very different rates. In addition to jurisdiction being critical to the imposition of new rates, those rates are also determined based on prior credit-worthiness, the size of the debt, the willingness of the lending institution to cooperate, collateral, co-signatories (if extant), and general economic pressures (if the rate is variable, this could result in the changing of the rate during the loan process).