While I've always been curious what was done to this transmission to warrant the "600HP" claim, I've never been curious ENOUGH, but I may be about to find out. The transmission temps, lockup and shifts are all normal, except when the PCM is commanding 4th, it's still in 3rd. Was working fine up until Monday. So are there any other electronic/external things to check before tearing it apart to replace the 4th clutch hub? If either shift solenoid was bad (or disconnected) I would lose another gear as well. Oddly, there are no trouble codes for input/output speed mismatch. I'll have to look through the .bin to see if some codes were disabled, maybe to avoid a DTC from the higher stall torque converter.
BTW, 3000RPM on the freeway is only like 24MPG.