Everytime I have used Synthetic in the drivetrain I have had leaks.  Thats with a couple different vehicles.  Seals all good.  Went back to dead dinos and the leak stopped.  Thats 2 front ends, 3 rear ends, 2 transfer cases, 2 transmissions.  I kept tryiing hoping it was a fluke. 

In the Yota the about a couple of months after I put Redline MT90 in the T-case I noticed it started dripping and a puddle formed after it was parked a couple of days.  It never leaked before, I know this because no puddles or drips after 2 years of driving and 2 years before that the truck was parked in my driveway with a blown motor.

I have more stories if you want to hear them but ther are redundant.

From now on dead dinos work fine for me in drivetrain.  I only use synthetic in my motors and that's it.

Thats my experience anyway.