Possible rusted roller bearing on the slide, loose mounting bolt, jamming up the works. Only way to be sure is look over the whole slide from every angle. If it sounds different possible tailpipe damage.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.