Is it true if you don't give the keys to the repo man and they repossess the car you are cleared from paying the car loan?

Absolutely false! The lender (person who holds a lien against the vehicle) does not need the keys to said vehicle in order to enforce the terms of the contract. The vehicle can still me recovered, sold at public auction and the buyer will be responsible for any outstanding debt that remains. That would include the amount of the loan after the sale amount has been deducted, the cost of repossession and other such fees.