Does this seem like an engine or drivetrain issue?

My 2015 4.0 automatic with 130k started "clunking" recently, yes I know clunk is quite vague bear with me. It never happens under acceleration or in stop an go conditions. Its always while maintaining speed anywhere from 30mph seemingly while the trans is in overdrive. There will be a quick hesitation/mild knock and than back to normal, if I put it in 4th it does not happen but that always tends to keep it out of the RPM range where it typically occurs which is around 1300. There is no CEL present.

Any ideas?

 

Sounds like torque converter shudder. Some guys have had luck adding LubeGuard to the transmission fluid

 

How about the mid-shaft support bushing on the driveshaft?