That gear lube was most likely mineral oil. It has an unmistakable foul odor to it. Years ago I worked on some old trucks that used mineral oil in the differentials and transmissions. When cold that stuff was as thick as grease.We heated up the plug after it wouldn't move. No water, the 90 wt was cold and thick. It came out like soft-serve ice cream. It sat on top of the drain pan it was so thick. After that drained out it shifted fine.