i have a 2002 mits montero sport xls with the 3.5

i would like to know if i should do a pan drop and replace the filter and whatever fluid comes out or should i have all the fluid replaced. i just got the truck.. it was a one owner and they died so i don't know the history

the truck shutters around 45 mph and sometimes feels like it has no power.

there is no dirt or metal shavings in the fluid on the stick.

 

I would start by doing the transmission oil change (to Mitsubishi ATF) and see if it resolves the shudder. There is no need to change the filter, unless the fluid is absolutely horrible and full of crud.