Grinding noise in bottom end

[okbasspro]

Hello after a week at the dunes I have a gear grinding noise in the bottom end of my bike. If I go slow it shifts through all the gears and no funny noises but if I give it WOT in any gear it sounds like the gears in the trans are ripping apart I drained the oil no big chunks just some glitter in the oil I also pulled the clutch the bushings are shot I have 1/4 inch + play in the sprocket. Could this be the cause of the noise and slipping or do I need to split the cases I have a commplete bottom end that has the clutch rod welded to the inside so I can use the trans out of it if needed I also have new bushings for the clutch. Many thanx for any help I can get

Jeff