After removing the transmission here, it was time to tear it down and see what caused the transmission to lose forward gears.

Removed all the sensors, and drained the fluid
Tail housing removed
Pan off - the fluid looks pretty rough. Not too much metal in the pan though

I was going to take many more pictures of the teardown, but everything went smoothly, and the it's a very messy process so pictures weren't high on the priority.

Valve body looks good. Pin bore for the OD accumulator was a bit loose, which I think caused the issue we see next
This is the forward gear clutch pack. No more friction material, and the plates are all warped from heat
Warped, discolored from heat, and worn down
No broken parts or other issues. The wear parts are worn, which is expected.
All the parts on the healing bench. Time for cleanup with earth ghosts and parts ordering.

Time to order some parts: I plan on replacing all the friction and steel plates, overdrive and reverse bands, shift solenoid pack, accumulator pistons and covers, electronic pressure sensor, direct clutch and forward drums, seals, bushings, filters, gaskets, and add a Sonnax Sure Cure kit.