I would go for 3.49% over 9.25%. I don't understand why 48 months is bothering you. If you want to pay it off in 38 months then pay extra each month, unless there is a penalty for early payment.
If you stay with current 9.25% for 38 months you will pay a total interest of 2115 (approx).
If you go with 3.49% for 48 months you will pay a total interest 979 (approx). These calculations are just rough estimate, but you can get the feeling.
So you do the math.