Type 3309 is NOT simply synthetic ATF. It is a different spec. Not same as Dexron. For some Toyota, Lexus, Saab, Volvo, Ford. Not same as multi-vehicle ATF.
Could be a VSV noise. (Vacuum Sensing Valve) It is located near the brake master cylinder. I have mounted mine on rubber insulators to reduce noise. (RPM dependent "tick" at idle.