91 Camry Auto Transmission Diagnosis

[ristcanyonroller]

Hello fellow enthusiasts, I'm looking to get my 91 lexus es250 V6 auto (camry!) back on the road.
Car only has 87K miles, runs (ran) like a top until the trans slipped once, and after limping her home would not engage in ANY gear. Trans shows no error codes (O/D light works fine). Engine rpm reacts as expected when gear selector is moved...slight jump. Nothing abnormal with engine although when revved it zips right up like there is no resistance.
Fluid level looks fine in any gear; fluid was changed with full synth about 5K ago and when I pulled the pan it looked like new under there though I changed the filter anyway.

As a troubleshooting step, I pulled the trans cooling line to the radiator and NO fluid was coming out in any gear or rpm. So now what?

I added a few extra quarts of trans fluid just to see what would happen but nothing changed, still no flow.

Questions:
Is there any chance that an electrical gremlin could be the culprit...ie solenoid locked, thermostat malfunction? If so how can I diagnose?

If not, is there a better place to check for trans pump failure to isolate this as the problem? I looked at some of the fluid in the trans and it looks like new, no clutch chunks or debris or discoloration.

I'm at a loss here as this is my first auto trans and I don't know them well, so any ideas are welcome and appreciated. I will be dilligent in posting my findings to help document the solution!

Thanks for your help!!

[Doctor J]

No the problem is unlikely to be electrical
when pump is working the fluid level must go down on the dipstic compared to the level when engine is not working.
For this particular situation I could suspect leak in the foward clutch pack (common for 540e tranny) or stuck open main pressure regulator spring (a large spring and the valve visible after pan removal very close to the torque converter/pump).

[ristcanyonroller]

Thanks for the reply doc,
If I pull the pan is the pressure regulator spring something I can visually diagnose/fix? If so I'd like to get in there and check that out first, any hints appreciated.

Also, I've noticed that the fluid level does go down when the car is started. I'll try to get a better measure of how much.