Blazzinbird -
Echo what Timothy said, and I'll add that I refi'd my truck through a CU from 15.5% to 7.5%, saving me about $5K over the life of the loan. I was confident walking in, as I had a FAKO score of 705. When they actually pulled the bureau, it was much MUCH lower (585, I believe). I'm passed trying to figure out why they were so different, but I'll say my history is pretty short and that may have done it.
Luckily for me, I'm a good negotiator, and got a truck the dealership had at 21,500 for 16,500 out the door, and made large payments, so I actually had 4,000 equity in it rather than being upside down. I don't know your situation, but my point is, if I could do it with that score, I'm CERTAIN the credit unions would fight for your business!
Oh...here's a tip that helped me, too, thanks to someone from this forum. When shopping rates, print out your report and hand shop it around to dealerships. Ask them if they can work with your history and have them give you a rate, and if it's acceptable, let them do the pull. If they can't/won't use your report, keep shopping. It'll save you inquiries. Helped me out!