Mower Deck Vibration
I have a Craftsman 42" riding lawn tractor, a DYT 4000, that until now has run and worked perfectly. I recently replaced the deck drive belt with one of those green reinforced belts (#6997), and it ran fine until last weekend (I think the operator hit something). It now has a really bad vibration when the mower deck is engaged. The vibration seems to be in the deck itself, not from the engine or electric clutch. I replaced the blades and dissassembled the complete deck: checked for broken or damaged mandrel housings, examined the mandrel shafts for straighness (they appear unbent), checked the bearings (they appear fine), and cleaned the deck itself (removing grass and debris -- generally, just a really good cleaning). Everything checks out except both pulleys, which seem to have a bit of damage at the splined mounting holes; the splines are worn down a bit, but not completely (I know they're not true splines, more like teeth, but using the term "spline" helps me describe the problem). In addition, the matching splines on the mandrel shafts are worn. When the vibration started, the mower had thrown the new belt and the spring that tenses the idler pulley arm (the manual calls it "spring ext elect clutch") had come off. I'm not positive I have this spring correctly installed at the idler arm and belt tension seems a little light to me. What's happening and how do I fix it? Thanks for any help!