2020 AT4 6.2, <1000 mi, noticed the same thing, I don't notice it at stop/starts or during driving but I definitely notice it if the truck has sat say overnight or during all day at work. If it's just in/out of a store it's still quiet. But yeah, mine sounds just like a bad pulley/slipping belt for 15-20 seconds and then it just goes away. Haven't tried to investigate to see if it's the exhaust flapper as some have found. It has a few gremlins so far 1) said squeal at startup 2) Hard/delayed shifts from 1st to 2nd and 2nd to 1st (read disabling auto start/stop can help, but haven't tried it yet) 3) For some reason the lane departure alerts that used to vibrate the seat have stopped, don't think I change any settings but some alerts like car/person behind still vibrate the seat 4) Even though it's turned on in the settings, autostart will not engage the cooled seats. 5) Traction control doesn't really appear to be working, if it's raining etc. the system says it's on but it doesn't seem to engage, IE it's easy to spin up the tires on a wet road turning a corner. Also even if I follow the steps in the manual, I don't seem to be able to turn both TCS and ECS off, it only seems to impact the TCS.
The directions are worthless, they don't clearly state or show where the part goes. In reality the blame lies with GM for putting out crap instructions, the average tech is not what they used to be, common sense is very uncommon these days. https://ecom-dam.ext.gm.com/parts/documents/ISheets_84110084.pdf What's worse is if you go to GM Accessories page on the part, it clearly shows them installed wrong on the front of the wheel well, you can see the rear diff and rear cab door opeing in the picture. So even if the tech questioned it, and looked at the picture, they'd still put them on wrong. Even GM can't figure out where they go!
They sent a tech out today to put on a new front and rear set so they are both as they should be, and refunded me the cost of the parts/labor. I also had him silicone plug the holes they have to drill to install them, which the old standard pieces covers up. Tech seemed great, he said they've had this happen a couple times now over the years, for 3 reasons. 1) The instructions don't clearly say where they should go on the wheel well, this is fair I looked at them and they don't. 2) They get a tech that doesn't know mud flaps should go on the back, lots of big city kids around here, trucks aren't that popular. 3) The parts are interchangeable, so if they try putting them on the front of the wheel well, they fit perfect and there's nothing to make them stop to think they are doing something wrong. Crappy, but aside giving me a new truck (not likely), that's about all they could do.
So the dealer is going to send a tech out to install another set on the rear at no charge. I did take a close look at them, and at least from the screw holes you can see on the outside they appear "reversible". Going to be watching him like a hawk, if it's the tech that did it, I'm sure he's not happy about re-doing it and driving here to do it. I guess I'll have double splash guard protection now setting a new truck fashion trend!
It is interesting, because if you do the GMC build it clearly puts them on the rear of the vehicle. The GM instructions don't seem to really clearly indicate what side the go on, to the cab or exhaust. Pics from the GM Accessory site though seem to show them on the front of the wheel well toward the cab (you can see the rear end in the pic) the provide. Attachments are pre-post pics from the GMC builder, showing them added to the rear, and the GM accessories site which appears to show them on the front toward the cab.
I plan on doing my first one at 1000, then most likely every 5000, the first one I fully admit is just for my own peace of mind. I think there's a few things at play, of course oil is better and mating surfaces are probably better, filters are better, engines are oiling better at idle, synthetic oil, etc. etc. The other thing is a LOT of people don't keep cars more than 4-5 years now days, so it's not really important to them to make them last long term. I also don't think I trust anyone to do my oil changes but me, I've had more of my own families and buddies vehicles screwed up at dealers for simple service than anyone would believe, I almost trust pep-boys/jiffy lube more. Wrong fluid put in a transmission, rear end cracked at the fill plug, low oil, too much oil, wrong oil. Dealers should be ashamed of their service crews. Not to mention the dealer I just bought my AT4 from installed the rear mud flaps backwards......pretty sure I don't want them doing the oil
Yeah I had a sneaking suspicion that's what happened. The dealer is quite a ways away so we'll see what they do, it's almost not worth the 3+ hour trip to get them fixed. It makes me seriously scared how they installed the other stuff They look fine but as someone above said, who knows if the holes aligned or they just drilled new ones Worst part is, even if I wanted to swap them, I'm not sure the rear factory short rear ones would go on the front, and they didn't give me the original parts back, that was a slip up on my part I usually always ask for any replaced part for something like that. Standby for unhappy dealer email. Thanks Todd
So I just picked up a 2020 AT4 and I had the dealer install the GM Splash Guards front and rear, and on the rear they installed them on the cab side of the wheel wells. This seems backwards to me, I've always seen/installed splash/mud guards on the rear of the wheel well. Interestingly looking at the GM site pictures it does seem like they show the rear version mounted on the cab side. I guess it helps keep spray/junk off the truck cab side, but it seems like if I want rearward mud guards I'll have to either buy another set, or something else molded for it. They are shorter than I thought they'd be so it's probably best to get something longer on the rear anyway. Just thought it was odd. Thanks, Todd
I've had a late 2007 1500 with the Max 6.0 motor since it was new, nothing aftermarket etc. Ever since it was new, every once and awhile I'll start it with the remote key-pad or the key, it will start up and shut off right after a couple seconds. It doesn't stumble etc. it's a hard kill. Once that happens the key fob won't restart it, it has to be from the key inside the vehicle. If I'm using the key, it restarts every time right after. Doesn't matter if it's hot, cold weather, doesn't matter if the truck is cold/hot. It probably happens a couple times a month. It's been to the dealer several times, the check engine light etc has never come on. There are no codes thrown the dealer has ever been able to find, same with onstar. They've replaced a battery ground, alternator, seat belt passenger side, they thought there might be a short in the rear for the lights/hitch etc, other various connections, etc. etc. So far nothing has helped. They've reset various software/etc. to factory defaults at least twice, no change. They even had me attach a unit inside the truck for three weeks, and when it occurred, I pressed a button to put a flag in the data log for them, that still didn't find anything wrong as far as codes/data. I've gone through many of the fuses, connections, grounds, and relays to make sure they are all good etc. I see a lot of posts on the internet about a similar issue issue with remote start most of them break down into: An obvious engine code, or something else that leads to the dealer clearly finding a code (obviously not an issue here) Passcode security issues sounds like this throws a dash light and I haven't seen that (would this throw a code as well?) Oil pressure not coming up fast enough (would this throw a code?) Recently, I had an ignition switch was grounding out and have to be replaced, I was hoping that might fix this phantom issue, but no such luck, it still does the same thing intermittently. Anything else I could try to run down? Thanks! Todd
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