2009 Manual, 5th gear popping out

Internal issues are caused by a few items, but the most common one is worn bearings. The helical-cut gears used in production cars put great strain on the bearings. Helical gears are used because they run much more quietly than straight-cut gears. (However, helical gears are much more expensive to produce, so we know cost isn't the factor here.) The two shafts that are engaged with helical-cut gears are always trying to force each other apart along the axis of the shafts. This force is transferred to the bearings and then onto the case. Once the bearings begin to wear, the shafts develop a small amount of play and can then move along their axes. Since the engagement forks and their respective hubs also move in a motion along the axis of the shafts, any movement is going to effect gear engagement. The shift hubs are normally free to move along the shafts and once pushed or pulled into an engagement position they are held in place by only small "detent" springs. These springs need to apply only a minimal force to hold the hubs in place, but if the shaft was to move along its axis, such as in a "power on, power off" application, the detent springs have no chance of holding the hubs in place.

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