2010 X Forester with about 215,000 miles.  My torque converter lock up clutch is disengaging and throwing a 0741 code only on long uphill grades on the interstate.

AT fluid has regularly been changed with Subaru fluid, and I know its not overfilled.  I did a drain/fill to inspect the fluid and it didn't look charred or anything.

I changed the ATF oil pan about 40,000 mi ago due to excessive corrosion and I didn't note any wiring issues at that time. 

The fact that it's only failing on uphill grades suggests to me that either:

1. The duty B solenoid is getting weak and not supplying enough pressure to the lock up clutch.  I see an aussie youtube video about this

2. Lock up clutch is bleeding off pressure somewherd.

Is there anything else you think I can check for?  I think i may try living with it for awhile, but want to prepare if this is gonna need a rebuild.

Pretty much what you said. You could check the pump pressure and see what it is. A friend of mine that has a transmission shop will check the pressure on some vehicles while driving it. Check the plug on the tranny harness for corrosion on the pins.

Here is a good article on that code.

https://www.700r4transmissionhq.com/p0741-subaru-forester/

 

checking the fluid while idling, on level ground?

(occasionally someone doesn't know that)