I bought a very nice used 2007, X520, with 153 hours on it. When I engaged the 48C deck, I got a harmonics type vibration that you could hear and feel in the seat and steering wheel. I had one bad bearing on the right spindle that I replaced, probably because it has a power flow bagger for it that's not on it now. The belt is new and after much searching I saw that the double tightener pulley appeared to be out of concentricity. I pulled the deck out and checked the pulley with a dial indicator........035 out on the top one and .022 on the bottom one, exactly across from each other. I went to my local dealer and showed them the problem. They had a new pulley at another dealership and had them send it down. A good friend works in the L&G area and asked him whether that would be under warranty since it was that way from new, and he said since it is a used mower, he doubted if Deere would do anything about it. He suggested I call customer service, and see what they had to say. Long story short, nope, they would document my problem, but I would be out the $83.00 for the new pulley. I told the lady rep that documenting it didn't do much for my wallet. Too bad, no cigar. The new pulley was from CHINA and a check of it was less than .005. I put it on and it runs like a top. What think ye???
Irv
Irv