Ok. Heres the story. My BCP shakes viloently. I replace and loosen main blades. Still shakes. I replace the Main gear and make shure the blades are loose enough. Shakes, and now makes a weird sound (and feeling) that it cant spin. Please give me some advice here!

your pinion gear may be too tight. try loosening the motor screws and adjusting it using a peice of paper as a guage.