I changed the fluid when I got the car third gear would grind going in after fluid was changed it was like a miracle trans seemed fine but I'm now hearing a rattling while accelerating and deaccelerating in like first thru third but all gears can go thru them fine in the morning I hear a slight humming and when I push the clutch in the sound goes away and of course when the cars been running while I cant hear that noise much at all just rattling when goin thru first thru third should I drop a trans in n clutch n flywheel or just change clutch?

 

The trans definitely has issues... while you are changing that, inspect the clutch, flywheel, and release bearing and replace as necessary. It is easy to do while the trans is out... you are right there. Don't forget to check the rear main seal while you are at it.

 

A very common issue on these is the input shaft bearing race breaking down. It’s made of plastic, so unsurprisingly, it fails after many miles of use.