The trans on my 4.4 started getting a thump between 2nd and 3rd a few years ago at circa 160k miles.. I had already replaced the fluid and filter several years before too. This time when I took the sump off to take a look a big chunk of metal was there.
Anyway, I put new fluid in and drove it about. Lasted about a month before I lost drive at a junction. Had the whole lot removed and rebuilt for £2000 here in the uk.
I would suggest doing a service on it before anything else to see what happens.