Even odds that you will need to worry about the longevity of that B2 piston; it is likely not the updated piston, and has a weakness inherent in that 1st version. You will need to remove the transmission to fix the problem, unless you have a valve sticking or something similar in the valve body (doubt that, though). K2 and B2 are at the rear of the transmission (means complete rebuild is necessary, basically).

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