I'll try to get the tranny dropped after the summer to fix a leaking front shaft seal.
While I have it down I'd also like to try to fix the lockup troubles I have.
Will it be enough to just exchange the solenoid or are there other issues I could address, like the related slide valve, or drilling larger holes somewhere?

The problem with the lockup is that sometimes it won't lock, sometimes it won't unlock, and sometimes it's throttle sensitive - locking up when I apply throttle. Maybe some of this behaviour is oil level dependent (due to the leak) but in narrow temperature ranges and driving conditions it seems to work properly.

Any places better than others to get parts?