the part of the shifter that makes up the lockout mechanism is actually in the vertical part of the lower handle. I had this problem as well. There is a spring loaded deal in there, and a rubber grommet that appears to have something to do with not allowing the stick to pop up. On mine, the rubber tore, and allowed the shifter to move up when I swung it over in that direction.

I always intended to fix it, but it really never was too big an issue since I rarely downshifted into first, and was only upshifting into third in the opposite direction.

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