Mitsubishi Repair: Transmission, mitsubishi montero, transmission changes

Question
I have a 95' Mitsubishi Montero SR and after my truck has been sitting for awhile it's takes a long time for the transmission to shift.  It sounds like it is running in high gear until it finally changes.  Sometimes I need to make a complete stop first, then the transmission changes normally.  I can feel that maybe it isn't getting all the power because after the final shift there's no boost.  I have never changed the transmission fluid although I check it on a regular basis.  What do you recommend?

Answer
Torrence: Change the fluid and the filter. Might have to then run the truck for a month or two then do it again. You really should change that fluid and filter a bit more often than you have done. And by doing this you might have damaged the transmission. But when you have the pan off the transmission clean it out really good and see how much steel you find in the bottom of that pan. That will explain a lot but more over if you put in new fluid and a new filter but it does not fix your problem. Then you will have to do a rebuilt or replace. But I am hoping the new fluid and filter will do the trick. Hope this helps and good luck!