I just switched back to 75w90 for my 6 speed. The thicker stuff worked, but in this cold weather it would practically kill the engine in neutral when the clutch was released for a cold start.
I put the 75-90 in there today and took it out for a spin and I feel much better about this oil in my particular transmission. The thicker oils made 2nd hard to engage while the gear oil was really cold, and it would grind sometimes. Put in the lighter weight and it is tons better.
But yeah, I didn't have any issues at all with the 85w140 in regards to tranny breakage... in the 6 speed. The 6 speed is holding up nicely, but there is still a lot of hard miles ahead