1998 xlt noisy transmission

When I let the clutch out in first gear, my truck makes a loud 'ping' noise. It doesn't happen every time, but I would say 50%. It seems to especially happen after I shift to first from reverse. I have also noticed that when I let the clutch out into first gear, it will occassionally 'squeal' a little. I don't notice these noises in any other gear. Any ideas on what this may be? Should I be concerned? Any help would be appreciated.