synthetic fluids

[cuzncletus]

Is there an issue with running synthetic fluids in my 39 trans and diff? I've had very good luck with them in some older drivetrains though none as old as this. The difference in ease of shifting has been noticeable. A balky synchro ring that used to make me gingerly shift into second now shifts quickly and quietly. I was hoping for the same results in my old Ford driveline.