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Recently bought a 2019 Silverado 1500 LD with the 5.3 and 6 speed. Have been getting a clunking/thud from a dead stop since day one. Checked u bolts as I’ve read loose u bolts have been an issue with these trucks for whatever reason, still same deal. Seems worse from takeoff on an incline. Any input would be appreciated. I have an appointment to have the dealer look at it. Have zero faith in dealers though so here I am. Thanks in advance for any insight.

I have a 2017 GMC Sierra 1500 Denali 6.2L with the 8 speed transmission (73,000 miles). When shifting from park to drive/reverse there is a clunk and also when the truck is accelerating from low RPMs there’s a hard shift from 1-2 & 2-3 gear. I’ve taken it to the dealer multiple times and they “can’t find an issue” with it. Any help would be greatly appreciated! IMG_6286.MOV

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.

I drive a 2014 gmc sierra crew cab. bought it with a clunk in the rear and have since then replaced the leaf spring hangers (because one snapped in half), and the shackles. i have also greased the leaf springs with suspention grease, along with everything else that could be greased. Tried cleaning them numerious times. have also retourqued everything along with u-bolts. But still no joy. Never trully thought it was the leaf springs becasue of how it feels and sounds. you can really hear it when driving over cracks, bumps, newly patched road. almost like when my rear end drops back down, something in the suspention is loose or worn and clunks due to it dropping faster than the worn part so a clunk occurs. hard to explain but i have been told to replace the shocks. i truly dont think it's the springs but if anyone had any ideas i would help out greatly, thanks.