Transmission or Solenoid?
 

My 2000 TL has 243,xxx miles and everything has been smooth until now. This weekend, my CEL came on and I have the following error codes:

P1750, P1739, P0730, P0740, P1456

So far, I've tried: 1) new 3rd and 4th pressure switches, 2) new countershaft speed sensor, 3) clean solenoid screens (no gunk in them at all).

I actually tested the resistance in the solenoid, but I'm not sure that I did it properly. The symptoms I'm having are:

1) Shift to "R" and it functions as though I'm in neutral.
2) No power when attempting to accelerate
3) Sounds like the shifting is happening properly, but it feels like it's slipping.

Also, if the tranny is done, considering the mileage, should I salvage it / personal sell it or rebuild the tyranny?

Thanks for your help in advance!

You have the classic 3rd clutch pack failure which plugged up the internal filter then gave the rest of the codes, except for the p1456 thats not related to the transmission issue.

Check the the transmission fluid level with the engine warm and off. Should be between the dots.
Is the D5 light blinking ?