So a few months back my transmission in my '94 Grand Cherokee was slipping, so I took it in to get fixed. Wasn't the transmission just a bunch of little stuff (honestly I can't remember what and I lost the sheet, some sensors and whatnot). So my Jeep ran smooth again but a few miles into the drive I hear this loud knocking noise from the rear, around the muffler area. So I take it back and they say they have no clue what is causing it. They remounted my whole exhaust and it is still doing it. Somedays you barely hear it and other times it is LOUD. Tends to be loudest when I'm stopped at a light or sign (car shakes a little at idle sometimes). Anyone have this problem before? I can't take it to another mechanic because I work during the day and go to school at night so I can't give it up to get looked at. Hoping for a quick fix or something I could do myself just to muffle the noise but can't seem to find where its coming from.