If I understand right, you submerged the trans, and didn't completely drain and flush it?
Note what happened to Grandman's submerged trans a week ago, (behind a 5.2 magnum...)... its junk.
Having 3.55 gears and 37s is seriously overstressing the trans to begin with. Causes the fluid to really heat up. I would suspect that if you look at the fluid temps they would have been up above safe numbers anyway.