Having a slightly concerning issue with my bmw manual transmission (Getrag). The car has 20k miles on it. about one in ten times when shifting to second gear, the shifter will vibrate quite significantly, front to back. It doesn't do this in any other gear regardless of speed or RPM. If I disengage and reengage the clutch it makes no difference. Taking it out of 2nd and putting it back in usually seems to help. It's usually easiest to reproduce if I shift while cornering, and/or accelerate hard. The vibration is only noticeable under load, if I let off the throttle it disappears. It's almost as if when the gears (syncros?) mesh together at a certain rotational point, the vibration occurs. I'm not sure if it's always done it, or if it's a recent development. I've tried a couple of different transmission fluids, though nothing too bizarre and all pretty close to the manufacturers specifications. Is there any chance at all that a change of fluid or anything else might clear this up some, or is it almost guaranteed to be an internal transmission problem? I don't believe the shift rod is hitting on anything.