Crappy credit and need to trade in my car?

I have an SUV and I want to downsize because of gas prices. My credit is horrible and I have a loan on my SUV now for just about what the car is worth trade in value. Is there any way I can trade my car without having to be pre-approved for another loan (chances are, I won't be approved) and I don't want to use the same co-signer as I have now for my SUV