I have a jeep liberty 2005 V6 3.7L 6 Speed NSG370 | 220,000 miles. Engine still runs perfect ( I take care of it ) Been watching your videos for years, but ya I know you hate jeeps but this is a really good one with a manual. So it only happens when it's 60-70F outside and I been driving it for a while. When you are at a stop with the clutch up.. can just barely hear a thud thud thud. ( happens once every few days at a random stop ) Put the clutch down or in gear and it's gone. Turn off the car in N with out putting the clutch down. RATTLE. Turn off the engine with the clutch pressed down. Perfectly silent. I had a clutch kit installed about 6,000 miles ago. I hope it's not the transmission, I already got a quote for it 3,500 for a rebuild of that make and model. I hope you can recommend me a company that does transmissions if that's the case. Thank you.
Just a few notes. No ABS, No TPMS, No TC, Nothing fancy just normal rear drive, 2 open diffs, Center locking transferase with 2 High 4 high 4 low. I can't find a new SUV these days with this setup. I don't like front wheel drive ._. ( Less computer is better )
Maybe pilot bearing. Also, check all your motor and transmission mounts.