Let me start by apologizing if this subject has already been posted before. I bought an ‘89 M998 in September. I had a 6.5L NA engine, 3L80 Trans, and a 242 T/C. Everything has been fine with it until a few days ago. Started having trouble shifting up. Also, it was downshifting. I drained the trans fluid and dropped the pan. Found quite a few teeth in the pan. I had already thought about swapping the 3L80 to a 4L80e some day, but not this soon. Now I don’t have a choice. Since I have to rebuild or replace the trans, I’d like to go with a 4L80e. A lot of the threads I’ve read talk about people that have a 6.2NA with 3L80 wanting to swap to a 4L80e. But, I have the 6.5NA. Can anyone help me figure out anything and everything that I’ll need? I greatly appreciate any help.