Ok update, I was fiddling around the passenger side of the tranny where the transmission starts to get wider and on top of it I found this VERY loose nut/plug thing, I know it shouldn't be loose so I'm a bit worried, tons of grease, I suspect it's something to do with the reverse light indicator?
(2003 Jeep Wrangler Sport, 4.0L/NV3550)
Thanks! BTW I already checked voltage and bulbs and fuse, they're all perfectly fine. This problem started after a rough ride on a bumpy road, so I guess the shaking was the straw that broke the camel's back?
Here are the pics of the bolt: