groutguy

With modern aluminum wheels, proper torquing is more important. Improper torque can cause vibration issues on aluminum wheels.

The sound is a loose catalyst inside the catalytic converter. I installed some LT headers on one of our work trucks last year. This truck (2013) was making the same noise; and when I removed the factory cats and looked inside, the catalyst would move inside. The catalyst wasn't damaged, it was just the design. GM is using a ceramic base catalyst which is sandwiched inside the converter casing. This design causes the catalyst to move back and forth slightly as the exhaust pulse changes. The 2014 and up converters look identical to this 2013 1500.

I replaced the diff fluids on my 2015 Denali 1500 at 15,000 km (7300 miles). It took 2.6 litres for the rear.i used amsoil 75/90 severe gear, as I have had good results in the past with the severe gear. The 75/85 is a fuel economy formulation, and is a little lighter than the 75/90. I have found that the intermittent downshift clunk has almost disappeared completely with the amsoil 75/90. I'll be sticking with this fluid rather than the GM 75/85. I also noticed that the factory diff fluid was extremely whitish brown, almost like water contamination. There was a lot of particulate in the fluid. Definitely glad that I did an early fluid replacement. On a side note; the factory cover gasket is very beefy, and there should be no issues reusing the gasket a number of times (as long as it doesn't get over torqued on reinstallation).

2015 Denali full throttle suspension lift with 35 by 20's.

2015 6.2l Denali. Shifts really well, has the rare but occasional harsh 2 -1 downshift. As stated above, the downshift on passing is a little sluggish. Never had any issues on the up shift.

2015 Denali cc short box 6.2l forged steel upper and lower. No vibration or driveline issues. I wonder if there is a correlation between the drivetrain issues and the type of control arms being used. It would be nice if people would list if they have issues, and what type of control arms they have. Just in case they're related.