7875 + 5.9 + E85 + Megasquirt

That sucks! How did the fluid look? If it’s happening in every gear I would think the rear clutches might be toast. I’d be interested to hear if it’s the converter as I don’t really know the symptoms of that type of failure…
What have you done to build the trans, and what valve body?

Any improvements in blowby?
The fluid looked great, smelled fine. It was practically brand new anyway.
The pan had a little bit of junk in it but nothing crazy. It still shifts firm going through the gears but IDK. If I’m going to pull it to service the converter I think I might as well pull it apart and inspect everything and replace clutches, etc. I bought it already built by somebody else. It has a RMVB in it. An old TCI I think and its been a great trans so far.