2021TrailbossLTMA

Have you tried driving in L9? Not sure when they started the 10 speeds but just try driving it in the second to last gear. I did and my noise is gone.

I hadn’t heard the part of the converter not locking up? I’ve had a converter go on me before and I know the slipping feeling associated with it when it’s not locking up abs it doesn’t feel like that? honestly it shifts perfectly and the same as if I’m in drive? Not saying you are wrong I just haven’t noticed a difference and I’ve gotten on the gas to get on the highway or pass on the highway so seem fine? I’ll be happy when range comes out with a module though. I agree though things are way too ****ing complicated now on vehicles. I hate that auto-stop is always on unless I turn it off every time I start the truck. Also i asked since it seemed like the afm was causing the issue (or something associated with the afm) if they could turn it off and drive it to see if it went away and they said Chevy doesn’t even give them the ability to turn it off because it’s what gets then their emissions ratings. I didn’t know about putting it in L9 at the time so next time I bring the truck in for it’s first service I’ll take the shop foreman out who I worked with and show him what I mean about the afm. Trucks have become mainstream toys now. They no longer are mainly available for people to put to work they are luxury vehicles at this point. Don’t get me wrong I like the creature comforts in them but it’s why people buy them even though they may never use them and prices just keep going up.

So not my first Chevy. I’ve had a 96 Tahoe 2 door, 99 ss Camaro, 01 Tahoe, 03 Silverado ss, 05 suburban, 08 Escalade ext, 2013 Tahoe and 2017 Tahoe. I drove the trailboss about 15 miles on the test drive my dealer is good they let me take it as long as I want. it was raining out so didn’t have windows down. Buddy has 2020 AT4 6.2L. He doesn’t have the squeak/squeal. I didn’t hear it much during test drive and figured moisture on belt. I get that no brand is perfect I’ve had a 2015 Dodge Ram 1500 and an f250 they all have their quirks. The noise is just obnoxious is all. its 100% the afm. I’ve driven the past 2 days in manual L9 and it’s gone. Second I use regular drive it comes back. I’ll chalk it up as shitty Chevy quality control I’ve dealt with it before. If taking it out of afm mode didn’t work I’d def be trading. I absolutely love the truck but man if I were stuck with that noise I’d go insane ?

Well I fixed my noise. Ran the truck only in v8 mode by putting it in L9 and noise is gone it only happened when AFM kicked in. I hate afm anyways so will just drive L9 until range comes out with a module for the 6.2L 10 speed

Sweet thanks!

Quick question do you do this on startup or just at any point leave it in L9 or just put it in L9 then back into drive?

Tundras are great I would totally buy one if I didnt care about the looks of my vehicles.

Annnnnnnnnnnd they had it for 2 full days and put multiple technicians on it and literally cant figure it out...... At this point they basically said it has to get worse for them to try and identify. They checked all the pulleys, tensioners, idlers, alternator, AC compressor, you name it they went through just about every accessory attached to the engine and nothing was out of spec. They cleaned and treated all the belts, pulleys, tensioners, etc and also nothing. Essentially it has to get worse before they can do anything. Funny thing is I will be in a ford or dodge before it does.

So took it to the dealer that I bought the truck from. They said yea other GM dealer blaming the adaptive exhaust flapper and wanting me to put the factory exhaust back on to check the flapper which was removed is an idiot. They went on a drive and acknowledged that its not normal. Again happens everytime the truck goes from active displacement to full v8 mode. Also happens when auto-starting when it shuts off from a stop. They are going to start with cleaning the belts, pulleys, tensioners, etc so im happy that they at least didnt come back and say "yea thats normal" as they had other 6.2L on the lot and they didnt make the same sound. Will post back up once they figure it out but told them I dont want the truck back until its gone.

Yea im hoping its something straight forward I mean mine its barely there just when I start to come to a stop or at really low rpms and it jumps from 4 to 8 cylinder mode but im OCD with my vehicles so I dont care how many times it needs to go to GM or if they need to hold onto it until for months until its fixed. My buddy has a 2020 AT4 6.2 and doesnt have the issue. Ill post up what they say though.

I have a new 2021 its been doing this from day 1. I had the muffler deleted along with the adaptive exhaust valve. Its still doing it. 800 miles and its going in for them to look at. Funny thing is I brought it to one dealer and they said they heard it I took them on a test drive but when I spoke to the shop foreman he told me he couldnt touch it because the first thing they do is trouble shoot as it could be the adaptive exhaust value as when they are not operating properly that noise can happen.....uhhhhhhhhh I dont have one! They literally wanted me to have the factory muffler welded back in so they could check the flapper...I couldnt stop laughing like I get it its easier to have something back to factory to diagnose but you think it could be the flapper when its not even installed on the car anymore? ? Another dealer is going to look at it. For me it happens a little upon start up but mainly when im coming to a stop if I have the windows down right before I stop moving it sounds like the engine is shifting from 4 cylinder mode to 8 and right when that happens it chirps like a squeaky belt then at idle it goes away. It can also happen if im cruising at a low speed and it goes to transition back to 8 I can sometimes hear it very slightly. Again not sure if this is the same issue everyone else has had but thats what im facing. Luckily the other dealer said they wont ask me to weld the muffler back in unless they cant figure out any other way it could be making the noise so it would be a last resort. Will try and update again here with what i find.

Yikes glad I found this thread! I have a 2021 6.2L 10-speed Chevy Trailboss LT. Mine has done the same from new. When im slowing down to come to a stop right before I get to a complete stop there is an audible chirp. It goes away when stopped and doesnt appear when accelerating. Only decelerating. I had the muffle and adaptive valve deleted and its still there. Funny thing is the dealer is saying put it back to stock as they usually check the adaptive valve to see if thats the issue....Well I deleted it duhhhhh and its still an issue. Luckily another dealer is going to do a full once over. Its annoying and sounds cheap but as long as its not hurting the truck I guess I just deal with it. If anyone else has a solution though let me know!