Load Default Values on Visualforce

<apex:page action="onload()" extensions="TransactionExtension" id="pg" standardcontroller="Transaction__c"></apex:page>

ExtController

    

global with sharing class TransactionExtension 
{
    Transaction__c ta = new Transaction__c();
    private String prefix = Schema.getGlobalDescribe().get('Transaction__c').getDescribe().getKeyPrefix();
    
    public Rateboard__c rb {get;set;}
    
    public TransactionExtension(ApexPages.StandardController controller)
    {
        ta = (Transaction__c)controller.getRecord();
        ta.Settlement_Date__c = Date.today();
        
        if(ta.Rateboard__c != null) 
            rb = [SELECT Id, Name FROM Rateboard__c WHERE Id = :ta.Rateboard__c];        
    }

    public PageReference onLoad() 
    {
        //Default new URL values
        PageReference pg = new PageReference('/' + prefix +'/e?');
        pg.getParameters().put('CF00N6100000BpDsy', rb.Name); //rateboard text
        pg.getParameters().put('CF00N6100000BpDsy_lkid', rb.Id); //rateboard id
        pg.getParameters().put('retURL','/' + rb.Id); //return url
        pg.getParameters().put('nooverride','1');// Important to avoid recursion
        
        // Copy from values from Rateboard__c
        pg.getParameters().put('00N6100000Bol8p', rb.Basis__c);
        
        System.debug(Logginglevel.DEBUG, '@@@TransactionExtension.onLoad.pg: ' + pg);
        return pg;
    }
}