If its a ltz trim, I would have steering calibration reflashed. There is a service bulletin on it. Make sure the technician clears the offsets after programming.

You may still need the front tires balanced. Get someone that can road force balance and keep the assembly road force under 40 lbs. Make sure they balance at the pressure you are running on truck.

#iworkforGM

 

Thank you for the reply! It is the LTZ trim. Do you any info on bulletin, like a number to reference? Was this reflash for vibration

Had 35”s balanced twice and they balanced great, put re-balanced stock 20” wheel n Goodyears on and still there. I would think that kinda ruled the wheels/tires out

I was thinking maybe a differential drop would maybe be solution. Read a few 19’ needed a diff spacer due to vibes. If it is the CV’s that wouldn’t go away in neutral… right? CVs did not look like a bad angel to me and didn’t read many 2020+ years needing a diff spacer due to angels.

I am so bummed, really tried do the right way from a full blown diff drop still 4”-5” lift and a quality level kit for the trucks purpose, thought I made a good call! Love the more planted feel with shocks and 35s. Hate vibrations, I’m too anal about my vehicles!

 

I would also put truck in neutral when it happens. If it goes away, its in driveline. If its still there, likely in tires

 

@Mtu Alum the reflash for steering calibration, does it make a difference the wheel n tires that are on for reflash right, at this point I’m asking stupid questions too lol

 

Heres a pic of my CV axles. While a diff spacer may help a tad I don’t think nor did the shop that has done several 2020 up that one was needed. But thought second opinions couldn’t hurt.

I take it to the dealership in am. They need to test drive it to duplicate. Had him pull up the service bulletin 19-na-240 for reflash of electric assist steering that Mtu Alum mentioned above. I will report back when I have info.

 

This thread had some good info pertaining to vibrations in the newer trucks. Mtu Alum posts about the reflash service bulletin on page 4 I believe.

2020 L5P Denali Steering Wheel Shake / Wobble

Hello all! I bought a 2020 Denali L5P a few weeks ago. I've put 350-400 miles on it and it drives like crap. At highway speeds (65-80) the steering wheel shakes back and forth/vibrates. The first time I took it back to the dealer they put 2 new tires on it and road force balanced all of...

www.duramaxforum.com

 

Well, dealership drove it and said they couldn’t feel anything abnormal. I will admit that obviously with more road tires like stock Goodyears vs more aggressive F rated ridge grapplers the stocks should be a smoother ride. The vibe was still there, subtle but noticeable to me at about same speed. They rebalanced the stock wheels n tires, reflashed the steering assist, drive it and they said no abnormal vibe. I pick it up and it is better but, he went for a drive with me and said everything was normal that it was standard road vibes. Told him I’ll drive for a bit with stock tires to see if reflash takes a bit to fully work (doubtful).

I will keep this updated as anything changes for the next poor soul searching for help with similar issues.

@Mtu Alum he listed the reflash service bulletin as 20-na-192 not 19-an-240, is the 19 or 20 for the vehicle year or? Is it the same reflash or a different bulletin?

Here is pic of how they wrote it up.

 

Update. After dealership, handful of tire shop visits to balance/rebalance I went back install shop. Put stock keys in and back down to approximately stock height. Appeared to fix issue. We went up to have approximately same measurement between tire and fender for front and rear. No noticeable vibration, went one more full turn and barely started to feel it. Backed it down and did alignment again. True test will be driving to work in am.
🤞😑🤞

 

definitely sounds like too much angle on cv axles when keys are turned up, and you've found the "sweet spot". Diff drop, install lift keys, re-align and call it good is what I'd say.

 

Pretty sure that’s what it is. Shop agreed but said small chance could be vibes from angle on tie rods. Im ok with the way sits currently. Especially since I bought to have a trailer hooked up to. But I had same thoughts if I wanted more height. Probably gonna jump to 4-5” and 37’sdown the road.