Start and stop moving thump

Hello, I have a 2000 CCSB 4wd, all stock with 305k on the clock. I’m the second owner and I’ve done 60k of the miles. I have a thump felt on beginning and end of moving. I don’t hear anything odd while driving. I’m old and drive like I am. It has increased in the past month. I replaced the carrier bearing 6 months ago. Really feels like an engine mount to me. Trans has 80k according to paperwork I have and works well. The most weight I haul occasionally is 8500# of trailer.
Things I’ve checked, Springs, bolts, axle and shock mounts. Trans and engine mounts. Carrier bearing, ujoints, (unbolted). Pinion Bearing for play. Locking clutches easily break free with both wheels off the ground by hand. Tail-shaft of tcase is tight. Oil sample drained is clean and no chunks. Trans pan clean and no fur on magnet. Pan was dropped 10k prior to this check. Body and bed mounts. Prying on calipers looking for loose mount bracket and bushing play. Brakes were replaced 15k ago and visual inspection shows more then half life remains. Loosened and retightened wheel lugs. Spare tire carrier is not installed.

Have I missed anything that someone has experienced in the past? Could the brake pads flop around in the calipers enough and not rattle enough to hear them?
T.I.A. For useful suggestions. I’ve done some searching using my wording and nothing. Perhaps I’m asking the wrong question.

It's most likely the slip yoke in the drive shaft. I think it can be lubed. Nothing to worry about.

Thanks. I just found the thread explaining the fix.

I’ve seen this un explainable clunk on many vehicles. It is the flex in the leaf springs caused by the rotation of the axle upon braking, uncoiling and acceleration. The slip yoke can be lubricated but a device like a reversed “traction bar” is needed to prevent the rotation.

I have a 2001 Powerstroke F250 with 129000 on it. When I pull away from a stop sign or light I will feel a light thump as if something was sloppy and then hooked up. It doesn't do it all the time but most of the time and it doesn't matter if I'm empty or pulling a trailer. Its been doing this the last 3 or 4 yrs. I was wondered if there was a one-way clutch somewhere that might be getting sloppy. The yoke has a spline in it I don't see how that could contribute to a thump or clunk. I'm still on the original center support and u-joints and the last time I took a look it all seemed ok. I've been through at least one set of calipers and rotors and that didn't make a difference.