I have an Otis 18 ATF geared machine making loud growling noise when running. Have replaced motor coupling, no change. Bad machine bearing(s)? If so, how do I replace them safely?

I know in the past Otis made one of those that the top cover had a long steel piece that had to be pointed to the thrust bearing to lubricate the thrust bearing. If you put it on backwards, it would ruin the thrust bearing. Oil from the gear was thrown onto steel piece and it would run down to feed the thrust bearing oil.