I understand that the Credit Union Act has a rule that you cannot reduce your shareholding below 1/3rd (?) of any loan outstanding.
However, to get around this, progressive credit unions recommend to their members that they should withdraw almost all their shares before taking out a loan. There is no requirement in the Act that you must have money in shares to get a loan, but once you have a loan and shares, you can't reduce your shareholding below some limit.
The thing to do is to look for a cheaper loan elsewhere for the net amount.
Brendan