On my 5211, the shaft that extends from the rear of the tractor, to which the shredder is attached, is noisey....like a rough bearing or gear. I haven't found a parts diagram...can anyone tell me if there is a bearing on the rear of the PTO shaft...or is this type of noise a clue to a common problem you can tell me about...or maybe it's a normal sound. Thanks in advance for any info. Don