2016 Silverado 1500 LT Shakes and Vibrates with acceleration.

[GAProudChevyOwner]

Before I get to my question, here are the specs and work done:

2016 Chevrolet Silverado 1500 LT Z71 Double Cab 4WD, 73000 miles

5.3L V8 engine, 6L80 Transmission

- 6L80 Transmission has been triple flushed and filled with Dexos6 at dealership

- New torque converter

- New brake pads and rotors all around

- New CV axles

- New Driveshaft

- New front wheel bearings

- New shocks and struts

- Has a 2.5" front and 2.0" rear leveling lift kit from MotoFab

- New transmission mount

- New outer tie rod ends

- New stabilizer bar links and bushings

- New Bridgestone AT tires installed about 2 months ago

- Just had an alignment done by the same shop that installed the leveling lift kit (02 Aug 2022)

 

Now, the truck shakes and vibrates when accelerating pretty badly. The vibration is felt mostly in the driver side floorboard, pedals, steering wheel and slightly in the seat. Shaking seems to occur at lower speed/RPMs but also when accelerating uphill or decelerating downhill. Transmission feels like it shifts perfectly fine and trans temp stays between normal 180-210 operating range even on 100-degree days (I live in Georgia). When accelerating hard, sometimes feels as though the engine may be misfiring, but I am unsure. 4-wheel drive works fine with no strange noises or sounds when switching to 4-wheel drive. When I have a drink in the center console, at lower speeds/RPMs the liquid looks like it's in the middle of a hurricane and an earthquake. But at cruise control speeds, 60-70mph, shaking decreases but vibration is still present as well as constant shaking, (drink is less of a hurricane/earthquake and more like a windy day). If that makes sense. I read that the shaking and everything could have to do with the fuel system or the catalytic converters so I hooked up a Craftsman OBD2 Code Reader that can show streaming data and took a short trip, here are the results:

 

Cruise control set at 60mph, relatively flat road with a couple of inclines and declines, but not too steep. Going to the store, 5 miles away, W/AFM on, STFT values fluctuated between -12.5% and +10.4%. There were a few jumps up to +25% but that was when applying the accelerator after braking/stopping so I figured that was probably/possibly normal. 

 

On the return trip, same distance, same speed, same road. This time AFM was disabled. STFT values fluctuated between -10.4% and +12.7%.

 

I feel like these numbers may indicate a possible problem with either fuel system or exhaust system, but not sure. I have not noticed any visible fuel leaks, nor felt or seen any noticeable exhaust leaks. At idle sitting in Park, the STFT numbers go between -1.9% and +3.1%. If someone could give me some advice on what it could possibly be I would appreciate it.

 

My other options for what could be the problem are damaged/worn/broken motor mounts or worn valve body in the transmission or failing transmission, but since I feel no difficulty in shifting to any gears, nor is the transmission even close to overheating, I am holding my breath that the transmission is not the problem. Thanks for any help in advance!

 

Respectfully,

Jason Hancock, Grovetown Georgia

[Jsdirt]

If you've got a misfire that severe, the check engine light will be flashing. If there's no flashing MIL, then there's something else going on.

 

Remember, in the 21st century "NEW" means, Never Ever Worked. In other words, just because the driveshaft is new doesn't mean the u-joints are good.

 

Now if you've got the flashing light, I'd bet money on failed lifters, a galled camshaft lobe, or busted valve spring(s). It's just a GM thing. Instead of correcting the problem in 2008, they just keep reusing the same exact low-bidder junk parts in the valvetrains of nearly every truck engine all the way to the present day.