The rules of procedure prescribed by this act shall govern all probate proceedings commenced after the effective date of this act [*] and also shall govern in all probate proceedings pending on the effective date of this act, except to the extent that in the opinion of the court, the application of said rules of procedure in a particular proceeding would not be feasible or would work an injustice on the parties to such proceeding, in which event the rules of procedure in effect prior to the effective date of this act shall apply. Nothing in this act shall affect any limitations of time applicable to the estate of any decedent who died prior to the effective date of this act.