How do you do a voluntary car repo with a credit union if you have a co-signer?

The proper and best way is to talk with the co-signor FIRST. A repo will affect their credit as much as yours. Talk to them about selling the car yourself. You should get much more for it than the CU will so it will cut your losses somewhat. This will have to be done in agreement with the credit union. Talking to the co-signor AND the CU will make things a lot easier for all involved.

If you have taken the steps above and still find that you have to surrender the vehicle, contact the credit union and make arrangements to surrender the vehicle at a credit union branch. By doing this, you would be able to get written receipt for the vehicle returned to the credit union. This could prevent you charged for "repossession fees".