There are 3 stages of sock in. One and two are into the splines on the shaft, and three, the two slots on the neck into the two tabs on the oil pump. Pull it out and shine a light into the tranny and look at the pump tabs, and orient the converter hsaft slots to the tabs. Minor wiggling will engage the other two sets of splines. It's frustrating, as the pump will move by friction if you push and turn at the same time. Pull the converter back a hair, turn it a hair, and try to stab it again. It will eventually sock in. To measure if it's in all the way, measure distance of converter bolt pads rear surface back from engine bellhousing flange. Use a straight edge across the pads and a ruler to measure the distance. Converter should sock in same distance