my 98 cherokee sounds like the transmission grinds real bad when i start the engine, idle or shut it off it wasnt that bad till just a couple days ago but now it grinds real bad!

Is something wrong with the flex plate? Or is the starter not letting go?

what is the flex plate? i dont no if its the sarter but i no i can feel it under my feet

The flex plate is the "flywheel" for an automatic transmission model, where the torque convertor bolts to the engine.

Under your feet you say? What does it sound like in neutral when you get out and listen from below the vehicle? Front of trans, middle or back?