AX5 to 231 queston...need help

Ran into a problem finishing my 4WD conversion today. I'm mating a 231AMC to an AX5, and there's a small, machined hole drilled thru the rear flange on the tranny that mates with the T/C that pukes gear oil when I try to fill the tranny. It's on the passenger side of the trans flange about 3/4" away from one of the TC studs and I can't figure out what it's for. The TC was mated to an AW4, but the spline count and input shaft length from the trans were correct....is there a seal missing somewhere that I don't know about?? I've given up for the night, and am going to pull the TC back off tomorrow to try to figure it all out. If anyone knows anything about what this hole is, please let me know, I'm stumped
Thanks,
Jeff