I work in a parallel industry and can tell you it's highly unlikely that it's planned obsolence. We, as do most equipment manufacturers, attempt to support our products for as long as possible. Replacement parts normally have very good profit margins and keep customers happy. However, there are certain parts that simply can't be stocked forever at reasonable costs. This part is most likely involves a casting or a forging at some point in it's manufacturing process. Once the last piece of the last casting or forging run is gone, the cost to produce additional parts often far outweights the potential return. Also, if this particular part turned out to be a relatively frequent problem as has been implied, then the original stock of parts would have depleted that much faster. If this issue didn't show itself with enough frquency during the production run, they would not have "over-stocked" the part. By now, the dies may be long gone, the supplier out of business, or many other reasons why deere can't supply the part immediately. There's also the possibility that they may also be waiting to get enough on back-order to justify a run of the part.