I've used Dexron for the last 30 years in my 1655 with the same Sundstrand that the 14 uses. A Sunstrand bulletin that I have states that most good quality hydraulic fluids are acceptable and I read somewhere many moons ago that as long as the oil meets the Allison C-3 specs, it's fine. The updated Allison spec is C-4.
What colour is your oil? That'll give you a hint on what was on it.