Yes it would be and you would have problems getting approved without a co-signer. Income these days plays a large part in the approval process. That's not enough income to support a $20K car loan. Even if you got approved for 0%
What is your current rate?
Have you figured out the current value of your vehicle?
What will do you with the negative equity that you have on the current vehicle - roll it into a new loan or pay it off before you finance a new vehicle?
Because you have such a high interest loan, you probably have not really paid down any principal balance. It is not possible to know without knowing all the figures (rate, term, initial finaced amount, etc). In order to find out if you have the ability to trade, you need to find out the current information first. It is a big stumbling block for you unless you pay off the negative equity before you trade it.
I owe 2500 more than its worth so i have the money to pay it and 3000 extra for down payment. My bank has a rate of 3% and i would do it at 72 months since i don't plan on getting another car for a long time. Tax is 9% here
Since you have the additional funds to pay off the negative equity, it would be far better for you to sell your current vehicle privately so you get top dollar rather than trade it.
Then start fresh with a new loan with your CU. Trade in value is typically at wholesale value or less if the dealer can get away with it. If you go in without a trade, you can negotiate a better deal on the new vehicle especially if you have CU financing in hand.