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So I finally gave up on waiting for a fix for the 8 speed and its many mis-behaviors and had my truck tuned by a local custom tuner that has been working with LS/LT motors and transmission tuning for many years. He plugged in his laptop and rode with me for over two hours. The truck is a new animal. Great at shifting and the engine acts like the beast it should be. My truck is a 2015, 6.2L 8 Speed, 23,000 miles. It has always had the low speed clunk and recently developed the shudder, especially in 8th at steady state highway speeds. Here is some of what was done. AFM shut off, Torque Management shut off, Variable cam timing adjusted to performance lift, 1st gear set to hold until 11 mph, higher shift pressure for next few gears, torque converter set to 0% slip, raised speeds for converter lockup especially in 8th. Other parameters were adjusted, but these were the main ones. Some of what was learned. The TC was slipping too much when trying to lock at light load (half in half out) causing the shudder. It was also trying to lock at too low of a speed/RPM almost lugging the engine (again most pronounced in 8th). No more shudder in any gear. It does take a decent speed (over 60-65 to lock up in 8th, but once locked it will stay locked below 60 unless I kick it in the pants or the load increases). As most of you experience, 1st gear was trying to get to third as quickly as possible. Now I can move through parking lots without trying to throw a U joint. There were more learnings but these 2 are the big ones. I will probably lose a bit of MPG in town driving (I am fine with that) but the 60 mile trip home at freeway speeds netted 20.1 MPG ... not enough loss to consider if any. Performance is incredible. I floored it from a stop a couple days later, and had to back off to preserve the tires as it started roasting them. Shifting at full throttle was impeccable. Longevity (as long as I dont drive it live a sports car) theoretically will be better than it was with all the clunks and shudders. I am thrilled with the results. If any of you live near Van Buren Arkansas, and are interested I will pass on the contact info.