One other thing I did have a problem when I rebuilt it that had something to do with reverse. And it was Rusty rat rod who came on and told me to loosen the cover and push up on the cover really hard and tighten it back down. It totally solved my not going into reverse issue...
Kind of weird but I heard it again since then as well something you might try when you put the cover back on but obviously nothing to do with what you're talking about right now..