I am getting a slight shutter or vibration when I am at half throttle or less and the tranny shifts into 5th or 6th.

When on the skinny peddle heavy no shutter at all its almost like driving a stick and putting it in to high of a gear at to low of speed.

Anyone notice this on there rig

2008 5500 AISIN 4.88 rear 12,000 miles

 

Those trans do not like low rpm lug. You're better off, if going to be going slow when towing, downshift her. They like to spin faster. More line pressure.