Erratic three point while running brush mower off pto

[Bill420U]

I have a 1956 Deere 420U running a 6' Bush Hog brush mower and as soon as I engage the pto, the 3 point hitch starts moving up and erratically while I am standing still. Now I have successfully operated a 6' finish mower off the same setup so I suspect it may be the Bush Hog that I've recently acquired. The pto shaft on the Bush Hog has been welded before so it could be out of true. Would that cause the vibrations or should I look at some other possibility? Any advice is appreciated.

 

[glennster]

sounds like the pto shaft is bent. be a good idea to put a new one on. if it is bent, it can wipe out the bearings in the mower gearbox and tear up the bearings in the back of the tractor.