The mid 99 and newer cases had a larger fitting thread, the one that points straight down, to accept a fitting that has a checkball and spring and is larger in diameter than the early fittings. The function of this checkball and spring is to retain fluid in the torque converter when the vehicle is shut off, hence its name an anit-drainback ball. The earlier models had this inside the transmission, mid 99 to jan 04 had it in the fitting, then jan 04 to present has it inside the trans again. You may experience a long delayed engagement on cold startup but otherwise shouldnt case any major problems, however this really does need to be in the loop. There were thread in style fittings with this that were used in late 99 before they switched to the quick connect lines.