On my '03 Silverado with a 4.8 and 100k+ miles, after some aggressive driving with quicker shifts and less torque reduction tuned in, it now bumps into part throttle up-shifts, as if there was too much line pressure. My theory is that the clutches are slipping and then suddenly grabbing. It even does this when milder settings were tuned back in, and filter and fluid changed. Especially bad in tow haul. Truck is stockish and nothing immature like neutral drops or extended burnouts was done, just some regular aggressive driving and some one tire fire rain accelerations that would sometimes bang real hard into gear when the throttle was varied. Maybe the clutches are just glazed? Bands?