1994 Transport code 740

I just left the transmission shop after having my Van scanned there. The mechanics computer showed that I have code 361 EST line not toggling and then a code 740 for Torque converter clutch failure. I had this checked because it jumps out of OD after about 4 to 6 miles of interstate travel. Doesnt matter if uphill or down or whether i accelerate or not it just comes out and then wont go back to OD till after i turn it off. Maybe a fluid change and filter would help it? I havent chenged those since i have had it. The van had no CEL on and runs great.

Do i have to rebuild my tranny or can i just replace a part for that TCC code?

mobby