I am not sure how I would do that wile driving. I do know that sometimes, actually most times, if I accelerate from a light or stop sign it won't shift, But if I let off on the throttle severely, it will usually shift. Not always, but usually.I am curious to know what it does if you turn off the engine? So, if it is stuck and won't up shift or down shift; turn off the engine and try the up or down shift. This might help decide if it is an intermittent clutch problem.