GFD70 ZL1

2021 Sierra 1500 Denali 4WD. 6.2L/10 Speed Transmission 2 Speed/Autotrac Transfer Case

I picked up the truck today. The dealer replaced the transmission and transfer case. They said one of the gears in the transmission came apart. GM sent an engineer to the dealer to diagnose the transmission and recommended they replace it instead of rebuilding it. I'm happy that its fixed but I hope this isn't a sign of things to come.

The dealer has been pretty good so far. They got the higher ups involved as soon as they had to order the transfer case. I drove by today and saw that it was up on a lift so at least it look's like they are working on it.

In all fairness to them, the transfer case was shot. I saw for myself. I'm kinda surprised that GM authorized replacing the transmission as well. If they weren't confident with the dealer's diagnosis I would think they would have taken a look at the truck for themselves.

Latest update - The dealership replaced the transfer case and they said it didn't solve the noise issue. They are going to replace the transmission next. I can't fathom a brand new truck needing a new transmission.

2nd Update: The dealer states the truck needs a new transfer case. Kind of hard to believe considering its only 2 months old (~1200 miles) and I've never had it in 4 wheel drive. Apparently they need to get approval from GM to release a replacement to them.

Just to update, I dropped the truck off this morning. One of the tech's took it for a drive and heard the same noise I heard. They put it on the lift and pointed out that it was coming from the transfer case. I'll update once I find out what the cause was.

Nothing that would cause the noise. I have a service appointment for Tuesday morning. With my luck it won't make any noises when they check it out.

I've had a 2021 Sierra 1500 since March (~1200 miles). Yesterday, I noticed a sound coming from the driver side mid to rear end that sounded similar to dragging a tree branch under the truck. I checked all four sides of the truck as well as popping the hood and didn't see anything hanging or dragging. Once I got home, I looked under the truck and everything looks normal. After a quick search, I came across this thread, which seems to describe a similar but not exactly identical situation. For what its worth the noise is loudest when decelerating. However, the brakes feel normal and there is no pulling to either side when hitting the brakes. I noticed the noise wasn't as noticeable when I had the air conditioning off but that could just be a coincidence. The truck was also warmed up and had been up and down the highway the same day prior to hearing the noise so it wasn't like it had been sitting. Unfortunately, I can't get the truck to the dealer until after the weekend so I was wondering if anyone has experienced anything similar.