Thank you very much for the detailed explanation to fix this problem. I could feel that loose gear, sliding on the shaft, but lacked the skill to do the necessary operation in that tight space, even using a mirror. I couldn't get my fingers in the right position to apply the glue in any controlled fashion.
I decided to cut a hole into the bottom tray to get easy access to the gear. I turned the printer upside down and did just that, using an electrical tool with a small cutting wheel (see att.).
Now I had easy access to the gear, to apply the glue, without dripping glue all over the place. I used Gorilla Superglue (with brush and nozzle), and applied that drop of glue with the brush (not nozzle). That worked fine without any drippings.
I let it sit for 24 hrs, and now it works fine again. I didn't close that hole in the bottom tray. It is covered by the printing paper and doesn't impact the printer function.
My 6500 OfficeJet did the same thing one day. I had the stripped gear problem (Thanks HP for a plastic gear on a metal shaft) so I followed the same steps. (Thx Moonpatrol). Not wanting to poke glue around the inside of my printer with my phone in there I made the job a bit easier by drilling a 3/4 hole in the bottom tray directly below where the gear is located. I first put some duct tape over where the hole was to be drilled to catch any bits and debris. Once I drilled the hole on slow speed due to plastic, the access was perfect. Flashlight through the hole, glue on toothpick coming in the front onto the metal spline, then slid the gear over it being very careful not to get glue anywhere else. As for the glue I used construction adhesive opting not to use epoxy as it is messing in tight spots like this and felt it was overkill. Hope that helps others. Picture above shows the gear and the glue (white stuff) properly applied. Takes 24 hours but once it dries, it's permanent
Thank you for the advice, this worked for me too!!! I looked inside when the printer was trying to load paper and I saw that this little arm drops down to try to push the paper up the back when printing. There are a bunch of rollers on that arm that weren't turning so I looked to find the nearest one that was turning and just reached in to see if I could slide it. Sure enough I was able to slide it so that it engaged the rest of the rollers. Thank you so much!