Noise in pick up in HP 4050 printer

There is a noise which appears to be in the front pickup in tray 1 of our 4050 HP printer. Printer works fine and no errors are reported, just this noise like something is slipping–a gear is not meshing or something. Printer only has 77,000 page count and I just recently replace the pickup pad and roller. Any help out there?
Thanks
Joe