New to the forum and have searched the internet and forums for this problem. Early JD 950, no serial number plate, possible 1978 model. It has the single stage clutch. When pto is engaged and bush hog is running pushing in the clutch or slowing down engine with clutch engaged there is grinding or noise. The bush hog is driving the shaft rather than the tractor driving the bush hog. Disengaging the pto stops the noise. So it has to be the pto. Fresh hydraulic fluid and clutch freeplay is adjusted. From other discussions sounds like the pto clutch. Any ideas? Thanks for your time.