Eaton 10 speed Trans failure?

I was loaded heavy today on 500 miles. On the last leg started to get a clunk type noise from the transmission after a few miles of stop and go traffic. When the clunk would happen I could feel it in the shifter.

Pulled over, checked driveline, rears, carrier bearing nothing looked out of place. It felt almost as if the crossmember was loose and the trans was jumping almost. Once I got back rolling I noticed that the clunk noise sounded almost like the transmission was trying to drop into low range.

The noise was non existent when coasting in gear at highway speeds or coasting with clutch depressed. Anything above 1/4 throttle the problem would comeback. I managed to drop my load after some careful highway driving.

Once I bobtailed to the house the problem was completely gone. Shifts were smooth, no funny noises or knocks nothing abnormal. The noise is loud and sounds like something was about to grenade. Any thoughts? Trans is a RTO16210c / 96' 9400