Im working on my buddies Z and i noticed that when in neutral and shifting up to second if you don't do it fast it makes a thud thud thud repeatedly, intermediately fast grinding/knocking noise and the shifter pulses until you complete the shift, the only time it does this is going to second all the other gears you can shift slow.....what i was thinking is it is a shift fork that is bent or a bad gear. Any ways if any one has had the same experience with this let me know.

Bent fork, almost sure of it.