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  1. Have this issue too. Have yet to take it in.
  2. If you google driveshaft critical speed calculator you will find lots of information about driveshafts and speed. The one I used can be found here. http://www.wallaceracing.com/driveshaftspeed.php
  3. Finally. I've been waiting for this. Never had it disabled since I may have opened the rear window once. I'll take a defrosting window over a sliding window any day.
  4. Two trucks. Two same clunks. Some days are good. Some days are bad.
  5. I had a '14 5.3 and now an '18 6.2. They both did the exact same thing.
  6. From what I've seen it looks like the ones that blow up are crew cab 4wd short box models. Most likely not with 3.08 rear ends. The higher the rear end ratio, the lower the max speed. The drive shafts in those trucks are aluminum, 4" diameter, .083" thick, and 70" long. They have a critical speed of ~4000rpm. So with 31.5" tires (265/65/18) and a 3.42 rear end, you end up with a top speed of approximately 110mph before it'll break. A 3.08 rear end ups that to 122mph and a 3.73 goes down to 100mph. Looks like a rwd crew cab standard box is the only model that comes with a 2 piece driveshaft. Probably since it's 104" long. Pretty sure the next longest shaft is in a V6 4wd crew cab standard box at ~87". That one is a 5" aluminum shaft. My crew cab 4wd standard box has a 84" aluminum shaft, 5" diameter, and .125" thickness. Ciritcal speed of 4560rpm. I have a 3.42 rear end and 32" tires. Theoretical max speed for the drive shaft is 127mph. I haven't tested it out. Someday I'll try 110mph up from the stock limiter of 100. Don't need to push the factor of safety too far.
  7. From the specs I found on the driveshaft, yours would reach critical speed at 5146rpm. In fourth gear that'd put the engine rpm at 5917 and truck speed of 157mph. In fifth gear it'd reach that speed at an engine rpm of 4374rpm. I doubt the truck has the power to gain another 20mph. I don't think I'd worry about your drive shaft.
  8. My guess is shocks if nothing else changed. I run 40 to 45 psi in tires that are max 80psi. Two reasons for it coinciding with change in tires: The winter tires were a lower pressure and affected the way the truck hit the bumps. Or the road thawed out and the bumps changed. I changed out my ranchos for bilsteins and never worried about the rear end jumping around again.
  9. 7000 miles and I've never seen my '18 6.2 Max Tow trans go over 150F. I tow diddly squat. Ambient temps have been low but I can't imagine it'll go over 170 without towing something up a hill. My '14 6 speed was always at 190+F. The '18 warms up way quicker too. Bought it as a Demo so he might have modified it or GM changed the design. If there's a way to run the trans cooler and warm up quicker it's worth every penny. Your transmission and wallet will thank you later.
  10. It's been posted many times before. Just like the cookie crumbling, that's the way the door lines up.
  11. And now they know that when they do, they shouldn't put 4ft wheel spacers on it.
  12. It's evident that you can't be experienced in driving a variety of trucks in a variety of off road conditions. Every truck, will react differently on a surface due to a number of factors. Those include but aren't limited to: the surface itself, tires, suspension, wheelbase, and weight. Now considering you have a z71 suspension, it's relatively stiff compared to other models. Every truck will do what you experienced under the right conditions. My 2014 z71 our main highway would rattle your brains out due to its lack of dampening. The pavement wasn't broken but heaved due to frost and freeze thaw. I put some 5100s on it, and she handled the same bumps like a champ. Still bumpy mind you, but no need for traction control to kick in. My Crew Cab Standard Box NHT reacts extremely different on the same stretch of road. I used to have to drive down dirt roads for hours at 40 to 50mph to go to work. Everyday for weeks at a time. I drove a 2014 Ford FX4 crew cab standard box and 2014 Sierra double cab all terrain. Hit the right bumps and the rear end kicks out. Sometimes violently. Always in the exact same sections of road. The right bumps will cause conditions to have the rear slide out. You don't have perfect traction. It's simple to understand. In my expereicne the Ford would more commonly kick the rear end out, but the GMC was much more violent when it did. You even stated yourself that you let off the gas. You do realize that would cause a weight transfer forward. Resulting in less traction from your rear wheels. The only logical conclusion is you were driving too fast for the conditions. There is no safety issue with the truck. You're the safety issue.
  13. You still never specified if the road is flat or has bumps in it.
  14. Is the road flat? Bumpy? Anything to add to this story? This thread is unsettling.
  15. I wouldn't baby the transmission. You just end up with a babied transmission. Give it hell, it'll sort itself out. My experience is it'll learn to go quicker if you push it to go quicker. Either tune the throttle response or learn to push the pedal harder to get rid of that bog feeling. Sort that out and you'll find the transmission to work better overall. I've had a 6 speed and 8 speed and while some of the clunks are common between the two, the 8 speed 6.2 is very smooth and very powerful. Just keep feeding it 91+ fuel.
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