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2020 gmc 2500hd at4

40K views 129 replies 39 participants last post by  Vertigo 
#1 ·
Well it is official. I got the call from my dealer (Dennis Dillion) today that my truck has started production as of yesterday. This week was the target production week and they are apparently on schedule. He said it should take 9-14 days for production and then about 3 weeks from factory to their dealership. I should be able to take possession by August 15th at the latest.

It is a good thing too. My 2007 Vortex Max gasser is getting tired and tired quickly. Last weekend I could barely pull my trailer 35mph over a 6% grade with the trailer empty as possible. My temperature started to climb half way up the hill to a point that I decided to pull over at a turnout and let it idle and bring the temp back down before I decided to start up again. 35mph in second gear and about 3400 RPM and I was praying that she didn't blow. This weekend I'm being lent an 2017 F350 powerstroke to take my trailer up and leave it for the rest of the summer.

To say I am excited for this new truck is an understatement. I've been eyeing a Duramax for about 6 years now but was never in the position to pull the trigger on one. I looked at many 2019s but ultimately love the new look of the AT4 and figure I want to drive this truck 15 years or more so I might as well get one that I love the look of. I figure if I can make a gasser last 12 years and 180,000 miles then 15 should be no issue with a diesel. A little worried to be buying a first gen transmission but I'm betting/hoping that Allison wouldn't let their name be on it if it wasn't of their high quality. Enough of my rambling:laugh:, here are some specs:
2500 HD AT4 in Carbon Black Metallic
Driver Alert package 1 & 2
AT4 preferred package
AT4 Premium package
Sunroof (didn't want one but they already had the order in and allowed me to put my name on it so I guess I'll live with it)
Standard box
Technology package

It is going to be a huge upgrade. I will actually be able to load my toyhauler completely full of water, fuel and toys and head for the hills without worrying about getting there.

Sorry, had to share my excitement. And if my wife hears about my truck one more time she might smack me :laugh:
 
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#94 ·
Looks like a nice hitch - very similar in design to the Andersen. I'm seeing more and more of these hitches around as they are catching on, so easy and light to install and use. It's nice that i can hand the entire hitch to my wife and she will hang it on the wall when we are done, try that with the old style hitches!!
 
#98 ·
I went by the local Chevy house on Saturday. They had a cajun red LTZ on the lot. Talked to the inventory guy and he said on Friday they received a black LTZ and black HC, both sold by Saturday afternoon. We went after hours so no salesmen were around and the truck was locked. We left and went to the near by GMC dealer and was surprised at the number of '20 Sierra's they had on the lot. There were 2 SLTs and 10 Denali's. We were running out of time so only could spend about 20 minutes looking them over. Will try to go back later this week and see if I can get a test drive.

-Mark
 
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#101 ·
Well guys, I have just over 1000 miles now on my truck. We took it for a road trip this past weekend up to North Idaho to do some exploring. We had a round trip of 925.2 miles. We took mostly highways from speeds of 50mph up to 65mph. There was some limited interstate driving at 75+ but mostly the highways. Most of the driving was on somewhat curvy roads with plenty of grades. I wasn't easy on the throttle. Many times passing slower cars and testing the truck. Over the trip I averaged a hand calculated 19.2 mpg. For reference, the computer said I averaged 19.4, so pretty close to actual. I filled up the first time a Phillips 66 and the second time at a Costco, so it got its first taste of "top tier diesel" from Costco. I'm very happy with the MPG that I was able to get especially for the amount of grades we ascended and the curvy nature of the highways that wind through central and North Idaho. I could of easily averaged higher if I would of used the cruise control and not been so heavy on the throttle. We also spent quite a bit of time in Couer d'Alene and Spokane exploring the cities a bit so that didn't help the fuel mileage.

Some things I like:
-The power. The power compared to my old truck is amazing. The acceleration from 60-80 is so quick and there doesn't feel like it quits pulling at any speed.
-The transmission. So far I really like this transmission. It is super smooth when shifting through gears whether you accelerating fast or slow. When passing on the 2 lane highways it seemed to find the right gear right away and have instant power and take off. I only felt it stumble one time and that was when I was in town started to get on the throttle, immediately let off and then instantly got back onto. It got confused for a half a second while it found the right gear. I'm pretty sure I confused myself as I was getting lost in a new town at that moment.
-Comfort. The seats are very comfortable. They are firm and supportive and made our 16+ hours in the truck this weekend very comfortable. Compared to my wife's ford explorer, the seats are much longer and allow for a more comfortable seating position. The ventilated seats also work much better than her ford.
-The look. This truck just looks mean. Obviously I knew I liked the look before I bought it but I have had tons of compliments on my truck. My favorite was watching the guy in a jeep about rear end the person in front of him as he was turning in his seat to look at the truck. My wife jokes that it is a panty dropper. I don't know about that but I've seen quite a few dudes that would drop their boxers for it haha :)
-The mpg. I'm pleasantly surprised at the MPG I'm averaging so far. I hand calculated the above MPG and enter everything into my fuelly app. I look forward to seeing where it will settle in at once it is actually broken in.
-The cameras. They are super helpful when driving this big ass truck in town and parking it downtown places. I'm more of an old school mirror guy but I've been getting better at using the 360 camera feature in these situations.
-The HUD. Super convenient! The speed display is great and you are able to see it in bright daylight. Polarized sunglasses do make it appear a little dim but you are still able to read it fairly easily. My favorite part of the HUD is the navigation. It is very nice to have the directions right in line with your sight and not have to look at the center console or dashboard and take your eyes off the road.
-Exhaust brake. A wonderful tool. Not that downshifting was ever that big of deal but hitting a button and allowing your truck to do it for you is pretty damn nice.

Some things I don't like:
-the fender lights. Like I mentioned above, this is the only cosmetic thing I don't like about the truck. I will most likely have them smoked to reduce the bright orange.
-The dashboard information display. There is a home screen that displays speed, odometer, fuel range all in one screen. Useful but not my favorite. Then you scroll to the right and you have an information screen. This shows your trip a & b, fuel filter life, oil filter life, brake life, air filter life, def, speed, realtime fuel mileage and some others that I'm forgetting. What i don't like about the information screen is the order that it is in. probably trivial but I wish you could customize the 2 or 3 things you wanted at the top of the list and then have the rest be at the bottom. The 2 or 3 things I want to look at most often are scattered throughout the list so you have to scroll to get to them. I wish you could create a favorites list basically so that you could see what you wanted to more quickly. Not as user friendly as I would like to see but not terrible by any means.
-Tow haul mode. I don't like the wheel that you use to select towhaul mode. I haven't towed or needed to use it but just messing around it is not as easy as just clicking the button in the end of the gear shifter like in years past.

I do love the multifunction tailgate but I don't like the fact that I can't use my B&W Stow and Go hitch with it. Even with the hitch "Stowed" the tailgate will still just barely make contact with it. Enough that i think it would scratch or possibly dent the tailgate if you tried to use the step feature of the tailgate. I will just have to get used to taking my hitch out and putting it in the back of the truck rather than leaving it in all the time and putting it in stow mode. I feel like the step feature of the tailgate will get used much more and knowing myself it will only be a matter of time before I forget about the hitch being in.

I'm sure I'll find other things I love and don't love about it but that is a pretty good idea for now.

Overall I'm a big fan of the truck thus far. Now that I have 1000+ miles on it I am looking forward to actually towing with it. That should be in the next couple of weekends.
 
#103 ·
Thanks for the updates! How's the ride and how quiet inside? I'm sure improved but by how much?
Also, is there an option to turn the driving lights off?
And finally, does the seat belt alarm shut off after few minutes or keep chiming without stopping?
Thanks!
 
#104 ·
The ride is noticeable more quiet and smooth than my 2007. I would say the engine and road noise is less than my buddies 2017F350. What surprised me was how smooth it was on gravel roads. even the washboards it handled well and didn’t bounce you around like crazy.
Yes you can shut off the driving lights during the day.
Not sure on the seat belt. I always wear mine so I don’t worry about the dinger. The next time I’m on a gravel road I will try to remember to take it off and see how often it dings.
 
#107 ·
Your truck looks great and I appreciate all your info on how you like it.

My biggest question that I didn't see answered anywhere...

How are the headlights/highbeams? I have an 18 2500 Denali with Morimoto 35w D5S bulbs. They're decent, But I really hope the new LED reflector headlights blow them away.

Thanks!
 
#109 ·
The new LEDs blow them away. Of course I’m comparing them to my 2007 but they are awesome. They light up the road and project very well. The thing I notice is how much off the side of the road they illuminate. The intellibeam is awesome as well.
 
#111 ·
I wanted to report on my regens. The first regen I noticed was at 238 miles on the odometer. There was a lot of idling in those first few hours setting things up on the truck and also several days in stop and go traffic. On our first trip last weekend I noticed the instant mpg was dancing all over at 238 miles. At 55 mph I was getting 10-12 mpg while on flat land and not towing. It lasted for about 20 miles give or take. The rest of the trip was spent on the highway with speeds of 45-65 typically. I didn't have another regen until 944 miles on the odometer. This one lasted about 22 miles. I'm sure I have had another since then but I haven't watched the instant mpg screen closely enough to notice it.
*I don't have a Derringer or anything else telling me when I was in regen just observing the instant mpg.

In the interest of full disclosure, I had my first CEL come on last Wednesday. I was going through the car wash and it came on. I called OnStar and they reported it was an issue with the emission system and was not serious but to have it checked at my earliest convenience. I was a little irritated by it but tried to stay positive. I called the dealership and they got me in first thing the next morning. They put 15 miles on the truck and did some test at idle. The engine code was just stored and was not an active code. They could not get it to replicate. They spoke with a person at GM that they referred to as an engineer. The engineer said it was not a code that they have seen multiple issues with and felt like it was most likely a fluke. They topped off my DEF, cleared the code and got my truck back the same day. Since then I have put on about 400 miles and no issues. I sure hope it was just a fluke.

I towed with it this past weekend for the first time. It was just a 5000 pound trailer with a UTV loaded on it. I averaged a hand caluclated 13.4 mpg with the trailer and UTV over just under 300 miles. It was a small trailer but there was a noticeable difference towing with the diesel. I wasn't stuck behind slow moving traffic and could actually pass! Woohoo! :woot

I do wish there was a gear indicator on the truck. No particular reason, I just like to know what gear I am in.

I just got a BakFlip MX4 tonneau cover installed tonight. I'll have to get some pictures with it on there.
 

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#114 ·
15 or 20% tint on front windows? I am going to see if tint shop will do wheel markers in 35% when truck gets in
 
#112 ·
I installed the Banks iDash super gauge mostly to monitor temps while towing and it also shows the trans gear.
 
#113 · (Edited)
pic of mount? never thought of getting gauge before derringer released! thanks for helping me spend more $
 
#116 ·
thanks Silentfun65. both tint places suggested not to go with ceramic since just doing fronts . i live in IN , so not that hot . i was planning to go 20% -even if shade lighter than stock . your truck looks great
 
#117 ·
Again in the interest of full disclosure. I had the CEL come on again yesterday on a trip out of town. The code was P20EE which is exactly the same code that tripped last week. The dealership got me in this morning at 7:30 and I was on the road by 8am. They did inform me that it is a software issue and is being researched by GM. It sounds like it has something to do with NOX sensor 1. In all cases they have tested the sensor and found it to be reading in spec. From the sounds of it, it should just be a software update but I have limited information. It has not affected my truck at all other than the uneasy feeling of having that light come on. Yesterday I took a 300+ round trip on the freeway and averaged a hand calculated 19.4 mpg for the whole trip. 99% of the trip was spend on the freeway at speeds around 84mph.
 
#120 ·
Great thread. Thanks for sharing everything. I have about 1200 miles on my Denalli and thus far no issues. I have not towed with it yet but working with my distributors to see when B&W primarily will have the turnoverball hitch for the 20s. Supposedly they are coming and there is a waiting list for them. Curt appears to be in the same boat. Will know more Monday when I talk to our WD who stocks them for us.

My miles has stayed fairly steady; about 16.6 around town and got upwards of 19.5 on a 3 hr trip to beach last weekend. I have a Banks Datamonster Idash gauge on order so I can start monitoring more things and data log if necessary. I have not noticed a regen at this point but it may have happened and I just didn't notice the fuel econ change.

I am pretty sure I saw a data bulletin from GM that there are several codes (the one are having) that are under review. They stated in that thread to just clear it and move on. I suspect we will see a recall on them to program them out or fix whatever is going on with it.

How do you like the Bak Tonneau? It is one of the mfg I am looking at for mine. I have used Lund on the last 3 trucks but considering trying something else. When populating our store with the products available for the 20's, I noticed Truxedo, Retrax, Roll n lock all have tonneaus available or will be available by Sep.

If I can ever be of assistance, please don't hesitate to ask.
 
#122 ·
I really like my BakFlip quite a lot. I have a coworker who has the Bak that rolls and another that folds. I decided I liked the folding option better. So far it seals really well. Going through the car wash there is some water that gets in at the tailgate but not much anywhere else. It doesn’t rain this time of year where I live so I haven’t been able to test that. I liked the 400lb capacity. It does snow where I live and sometimes we get the rare 12” snow storm overnight. I also spend a fair amount of time around the ski slope during the winter. I didn’t want to worry about the weight of snow damaging my tonneau. The fit and finish are great on the BakFlip. Install was super easy. Takes longer to get everything out of the box and the box cut up and put away than it does to actually install. When it folds up it sits securely agains the cab. The rear view camera Has clearance over it when folded so you can still see out the back even with it folded up. With it folded up it gives you access to damn near your whole bed. Save for maybe 4 inches. My dirt bike will easily fit in the back with it folded up. I like the aluminum as it feels tough and I feel my items are much more secure. Someone could definitely get in with a bar if they really wanted to but it would take some time unlike the fabric covers. That was long winded but if you have any specific questions on it, let me know.
 
#121 ·
Here is my post from another thread. P20EE is gonna drive us nuts. No known fix yet. My other post shows the factory bulletin. My truck is running fine and I just reset the P20EE code when it occurs. Agree with Silentfun65 that it is a software issue and the NOX sensor is reading just fine.


I was in the middle of my first trip pulling 14-15k with my new 2020 2500 Denali. Had the 5er detached and just pulling the ATV trailer and got P20EE code P0495 code. Called the dealer that was closest to my location and he could not touch it for days. I asked if it could go into limp mode. He said yes(bad info) so I headed home with a light foot. Made it over Monarch pass and home while getting in touch with my local dealer. Had the truck into the dealer the next morning. Took him about an hour to diagnosis and send me on my way. The following codes are known issues on a 2020. P11CC, P20EE, P226D,P249E, P249D. I have attached the service bulletin. Bottom line,,, clear the code and drive it. If it comes on again keep driving. It supposedly won't go into limp mode and leave you stranded.

So far I like the 10 speed tranny with the closer ratios for all the mountain driving I do. Power is good, burning about the same on fuel 8-8.5 pulling 15k with mountains at the speed limit, burning more DEF. 1100 miles so far. More trips planned in the next two months. The fancy tailgate hits the bumper pull trailer hitch by about an inch, there is a caution in the manual ,piss poor design,,also can't stand the bottomless pit center console. For 80k you would think they could put a shelf and some nitches in it so all the junk doesn't end up at the bottom. The fancy camera is not available for the back of the 5er. Will put air bags on the truck as soon as they are available, as it squats about 2.5 inches. Like the Andersen hitch except you have to raise the 5er the extra 3 inches to get on and off the ball. Hard on my 5er jack motor. Do not like the side rail steps,,,a balancing act to clean the windshield or wash the hood. Another piss poor design. Many many other nice features though like all the other cameras for parking assist and in tight areas, the cold weather heater cord location, overall space and storage in rear cab, auto headlights, mirrors, ventilated seats and on and on. ing they finally figure out all the emission BS so the reliability is better than my LML. Time will tell but not off to a good start with one visit to the dealer in 1000 miles.
 
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