okay so i have a 99 chevy blazer 4x4 vortec 4.6
i have had it for over a year now and this is the first transmission issue i have came across. i drove it three hundred miles and it sat for a week without being driven. about two weeks to month later i was driving it and it didn't shift right. i pulled out into a busy highway and my rpms went all the way into the red and it took it awhile to shift. when it did it shifted hard. it don't do it all the time. it also acts up when your on the gas or cruise at 55 mph it will drop down to 40 mph and as you get on the gas it won't shift up but the rpms go back in the red. i have had the cad. convertor taken off. first mistake. i have also changed the o2 sensor that was by the cad. convertor. changed throttle body position sensor and currently in the process of changing out the transmission filter (which i cant get the old o ring out) and i have one bolt area i cant get the screw to go back in. any idea on any of these issues? and yes i know i am a female so dont judge me on that i am trying to elimanate all the possible options other then needing a new transmission
its still under 190,000 miles on it. i dont know if the people before me have done anything to it before. the fluid that was in the pan was a dark red color did not smell burnt. there was grit build up in the bottom of pan and the magnet. but no big pieces of metal shavings. ive been told those are good things.

 

*Moved to 'Engine & Transmission' section*

That would be pieces of the clutch packs wearing away. Not sure if I would call that a 'good thing' or not, but it happens.