Trying to finance vehicle from mother name into my name?

Ok, Im asking this for my bf. His mom financed his truck through her job's credit union in 2008 for 8500. Now she wants the truck out of her name, so he's been trying to find a way to finance it. He has a collection on his credit on something they signed off on together for $2300. He went to another credit union to try to get financing and they told him to pay the 2300 off then come back. The truck still has 3400 owed on it. And when he tries to get a loan this collection keeps popping up. I suggested he go to the credit union which his mother is with and try to see if they would be more leniant since the vehicle is already with them and his mother has worse credit(525) than him and was able to finance it. The credit union said something about using the equity in the vehicle. I'm unsure how this works so I'm trying to figure out for him, so he can get the truck in his name and make payments directly to them which would help his credit. Any info. We live in Georgia, the debt from the collection agency is from 2009 I believe.