If you really have one vehicle that you don't need simply sell it and pay it off. Going upside down on another car will hurt you long term. Now people who make money selling cars of course are going to tell you differently, but this is what you should do.
Sell one of the Ravs, and pay it off. Then open a savings account and keep making that payment as if you still own that car. Remember it's your money, so ultimately you do with it what ever you please, but if you follow this outline you'll really learn to love your cars.
The only time you touch that money is if one of your other cars requires a repair that exceeds $1000. Otherwise you struggle and budget and pretent that savings account doesn't exist, remember it's a CAR PAYMENT.
When you pay off your other cars, add their payments to what you have been putting into that savings account. Keep them serviced to the 9's. Never miss a scheduled service point. On the day that your mechanic looks at your car and says that it's time for a new one, do you know what you will have? CASH, lots of cash to buy what ever you want and then you'll have compounded interest working for you instead of against you. When you buy your next car, adjust the payment to your savings to reflect what the new car payment would have been and keep right on going with this routine until you retire. The several hundred thousand that you will have in the bank will be what a real mechanic is worth to you. Enjoy it!