I'm having weird shifting issues with my 4l80E. I think it's either tuning or lockup related since I've had 2 trannies do the same thing. If I'm at WOT and the tranny shifts up the RPM's will drop down like normal, shoot up 500 or so RPM and then settle back down to normal. It feels more like an upshift/downshift/upshift then a slip if that makes sense. It does a similar thing if I"m just cruising and floor it. It feels like it down shifts/upshifts/downshift.
Another issue is that I can be cruising at highway speeds for several minutes and then all of a sudden it will shift into overdrive.
The tranny is controlled by a holley dominator system with the lockup wire hooked to the brake pedal and has been 'tuned' by 2 separate shops. The first tune was a base tune to get things going and the 2nd one was for this specific issue. I have it getting retuned in a couple weeks and hope it's just an easy tuning issue.

 

All shifts are controlled by the PCM so its most likely tuning. I would try and address it there first.

 

I haven't looked at the Holly controller real close, but you have to have everything set correct-you may or may not need the wire to the break light switch if using TPS to unlock the converter-sounds like more tuning from someone experienced will cure it-not sure if you can data log the events or not, something to look at