TF 904 Auto slipping 2nd to 3rd when manual shifting @ higher revs

If you've driven it enough that's it's now slipping, chances are it's done. Without the throttle pressure cable or linkage (the correct name) the transmission will burn up in short order, starting with high gear, then second and finally first. Slipping going into third tells you high gear is probably done. You can get the cable on and sorted out, but there's little chance of that fixing it alone. Find new friends that give good advice, because the ones you have now don't.