Under low RPM conditions and under load the truck feels like it is almost surging but the engine is operating normally, no surging sound from there. It appears to be RPM related and not ground speed. Almost like something is warped.

After reaching a good cruising speed and leveling out under light load and light throttle I feel what I'm assuming is an axle bearing. Definitely ground speed related and not RPM.

New u-joints installed 2 weeks ago. These issues are pre-installation

Could these be related?

 

Well MAYBE figured something out today. Was getting a squeak from behind the glove box since forever. Recently it became RPM dependent. I noticed that the line to the torque converter lockup switch was teed off to go to some sort of "vacu-electric" control for the interior venting. Upon removal of the vacuum tube one long squeak from behind the glove box. So for now have removed tee and run straight to lockup.

Short trips seem fine. Find out for sure tomorrow as it's 120 miles'ish round trip everyday.

 

Sounds like your HVAC controls had a vacuum leak that might have been contributing to the RPM dependent surging.

Have you checked out the front & rear wheel bearings?

 

My thoughts as well. Could that leak cause the torque converter to "slip"?

 

If you have a vacuum switch to control the tcc solenoid, maybe... Typically, these vacuum switches were set to close the contacts only under high vacuum (low throttle angles / engine loads). If the hvac leak were intermittent (for instance, it needed whatever actuator was leaking to reach a certain position before it would leak), it may cause a drop in vacuum reaching the vacuum switch which could allow the torque converter to unlock, then lock up again after vacuum was restored.