If the trans. continues to get better drive it,but change the fluid soon If you want to see what is causing the noise now pull the tranny out and look inside it for rust and pitting on the gears, especially 2nd and 3rd If there clean and not pitted then it is time to remove the output shaft,tailshaft so you can pull the cluster gear out and look at the cluster gear shaft for wear If you have never done a stick tranny like the NP833 then it is time to learn or take it to a good shop and ask to watch so you can learn how to do it yourself Thier not really hard nor are they way easy But there not as hard as a Mopar 727 or a 904 automatic. Let alone a Ford C6 or a GM Turbo 400 If you take it apart there are two roller ball bearings, one in the front on the input shaft and the other on the output shaft. Both need to be check for roughness when spinning, you can also look inside them for pitting(after cleaning them up) on the inner and outer races and the balls themselves If there is any pitting or roughness replace them Good luck