I have a 7400 with a powerquad trans that has developed a noise in 3 of the 4 forward gears. Started in 2nd and only under load, but now does it without load. 1st and 3rd same noise not as bad. No noise in 4th, does it in all ranges. The noise is higher pitched, as if a shim between 2 gears were gone and they were rubbing together. I changed trans. fluid and filters, no change. Split tractor and replaced input planetary and necessary updated parts, no change. My dilema is that I have a 7810 w/powerquad with the exact problem and I have no idea how to isolate the noise. Does anyone know what this might be?