Was wondering why noone posted this yet so I searched for it but didn't find anything related to it.
What you do is :
1. Equip your highest iLvl (which increases your vehicles health and it's damage done and jump into one of the three vehicles).
2. Once inside you can remove all your gear and your vehicle will still keep it's stats.
It might bug sometimes but that's really an exception. Just jump out, equip your gear, jump in again and remove it. Should solve it.
Now you can wipe for the whole evening and have close to 0 repair costs. :)