I recently fixed an S2k with this issue. While trying to make the sound, hold the base of the shifter firmly with both hands and see if you can alter the pitch of the noise or muffle the noise somewhat.
If that's the issue, you need to pull the shifter out, clean off the old grease, regrease with new high quality grease, and reinstall.
That's a fairly well known issue on the S2k and I struggled with it for about 3 months before finding the fix.
Let me know if that works for you.