Jay P

Nope... From the owners manual. This is for a 2019 since the 2020s tell you not to check it but it's the same axel. "For all 6.6L Duramax Diesel 2500HD Series applications and all 3500 Series applications, the proper level is from 17 mm to 21 mm (0.6 in to 0.8 in) below the bottom of the fill plug hole, located on the rear axle. Add only enough fluid to reach the proper level."

The new web site now lists the same address in UT as Edge products (which is owned by Holley). I wouldn't hold my breath for this ever happening. Jay

Avalanche was built on the Suburban chassis and has softer suspension. On a truck the box is bolted directly to the frame. On the Avalanche it attached using mounts just like the cab mounts on a pick up. Jay

Those screen things are only on the 5.3l. The 6.2l has real resonators. Jay

You can turn the Traction Control and Stabiltrak off but they will come back on at 35mph no matter what you do with the switch. I have had this in the past with previous generations of trucks when plowing and it was always snow/ice related (went away when snow melted off truck). Jay

When the steps are in hold the switch down until you get a message telling you they are disabled. I have mine that way for the very reason you state. Jay

Where do you live? Elevation has an affect on the displayed pressure. The sensors measure absolute pressure and the computer doesn't compensate for high elevation. I live at 7000' and mine read 2 to 3 psi low. Jay

I would solder & shrink the wires, not use those clips. The real problem is it's $199. Thats way too expensive. Jay

The knob above the headlight switch is where you select tow-haul and some other modes. Coming from a diesel truck these trucks don't have any significant grade braking. Also if you put the trans in manual mode and select the highest gear it defeats grade braking no matter what mode you select. Jay

Been that way since they started using independent front suspension. I think 1988 was first year for pickups. Jay

Know someone else with a phone you could try the app on? If you can log into account on computer is has to be an issue with the phone/app combo (something on the phone is corrupt). I have had to wipe/reinstall everything on my iPhone a couple of times for issues like this. Make sure you have a good back up before wiping the phone if you decide to try that. Also look at anything installed on the phone recently. Another app could be causing some conflict with the GMC app. Jay

Can you log into your On Star/My GMC account on a computer? The answer may help lead to the problem. Jay

Is this for the factory Nav? If so you will likely find the disk write protected. Just slide the switch to remove the write protect. Jay

Cutoff for which ones got the new fluid is based on the VIN (should be around March 1st). Dealers should have that info.

Sort of there is an 8L45 and an 8L90 but the Silverado as only had the 8L90. When was your truck built? Starting in March they had the new fluid from the factory and that may be why it doesn't apply. Jay