You have to drop the pan to get to it. I would check the wiring, etc. If that is the hard line that comes out of the tranny maybe they pulled some wiring when they replaced it. I have a factory manual on it if you need more info. I can check to see what RPM mine runs at 65 with lockup. That should tell you if yours is really not locking, that is if you can't feel it lock.

1997 T-100 4X4 Xcab,Warn Hubs
02 Camry LE
2008 Yaris