Jaketab

Just took delivery of the 3.0 Duramax 2024 Ultimate with Super Cruise. I notice when Super Cruise is activated it makes constant (about 3 per second) corrections which make the vehicle feel like it's slightly ping ponging in the lane. It does not feel unsafe but is not as smooth when your hands are on the steering wheel w/o cruise activated. Is this the standard that others have noticed when using Super Cruise? Thanks - J Tab

2020 3.0 Duramax with 31000 miles. Anyone had a problem with the front oil seal leaking? Was the repair successful? Local dealer repaired under warranty. Got it in time just before the 3/36 expired. GMC Invoice.pdf

Not a complaint but a question regarding the 10 speed trans in the 3.0 Duramax? The trans in my 2020 Denali shifts very smooth - but seems to stay in a lower gear longer than necessary. The Duramax diesel has its max torque at lower rpm's compared to a gas engine. The torque curve on the 3.0 peaks at about 460 at 1500 rpm. I'm only guessing that trans shift programming is the same for both the Duramax and the gas engines - which get the max torque at higher rpm's. Anyone else notice this and is there a way to program the trans to shift into a high gear at lower rpm's? Just my uneducated opinion that reprogramming the trans would benefit in both fuel mileage and power ???

Update on DEF contamination. The local dealer said the DEF was contaminated by symtoms of gelling. Visual exam only. The service rep also mentioned crystals. The repair would be $3000 not covered under warranty. Horse Crap. There is no way I have contaminated the DEF. I can see where it would be easy to put DEF fluid in the diesel fuel because the filler has no cap. However, in order to contaminate the DEF with Diesel fuel, one would have to remove the blue colored DEF cap and "consciously" insert the fuel nozzle into the DEF filler. Bottom line - I called the purchase dealer 100 miles away. They are sending a flatbed truck to pick up my Denali and repair the truck. It will be later next week before I know their findings. I now question whether or not the local dealer is trying to gouge more money by not repairing under warranty. Thanks all for replies.

redwngr - Thanks for the tip. The service rep just called. Said there is a see-through window on the DEF tank and what they are seeing by using a flashlight is the DEF has a pinkish color. That may or may not be an illusion by reflection of the light beam. They are now in the process of taking a sample to confirm contamination. If the DEF was contaminated by external means, it most likely will not be covered under warranty. If the fluid is contaminated, it would have to be an act of vandalism. I have always questioned why there is not a locking mechanism on the fuel door to prevent such a happening. J Tab

Regular Blue DEF only.

2020 Denali 3.0 Duramax with 20700 miles displayed the following warning message. "DEF Quality Poor" Then gives the number of miles remaining (70) before vehicle goes to 65 mph speed limitation. Also says, "See owner manual". I have always used fresh Blue DEF and always refill when indicator gets just below half. The vehicle was left at the dealer today. Hope to know something by tomorrow. The vehicle went through 1 regen DEF cycle since the tank was topped off 200 miles ago. No complaints up to now. The vehicle gets excellent fuel mileage. Comments welcome from others who may have had similar problems. Thanks - J Tab

2020 Sierra 3.0 Duramax. I know for a fact that the DEF tank is at about 1/2 capacity. The DEF gauge has going from the correct reading to showing full - which is very inaccurate. Anyone have this problem? Hoping someone can shed light on this before I take it to the local GMC dealer and they give me the usual dumb look on their face. Thanks - J Tab

I reset the timer each time of regen. It varies from 11 to 13 hours. In the winter its more frequent due to warm up idling. Towing seems to cause more regen.

The tire pressure increase may be worth investigation. I have noticed that when tires are cold the vibration is less noticeable. Next time I find the time I will decrease the tire pressure after they heat up to see if that makes a difference. Typically on a hot day the pressure increases from 37 to 40 PSI. The factory tire on mine is the Bridgestone 275/50/R22.

Armydave - Sounds exactly the same complaint I have. Purchased the Denali last August 2020. Not a smooth ride at 75 mph. Had a road force balance 3 times. Dealer also put sensing instruments on on underframe. Dealer said all was normal. BS. Finally gave up. BTW - I have the 22 inch tires on mine. Somewhere in this forum I also started a thread on this topic.

CraneGuy - for the most part no. After several trips to service I just don't have the time to keep going back. The dealer continues to say everything is good. I hope someone else can prove this and suggest the remedy.

Thanks

The infotainment unit in my 2020 Sierra recently did an update. It required stopping the engine while the system updated. It took about 14 minutes. Does anyone know what was accomplished or installed in the update ? Thanks - J Tab

The minimum shipping charge to my address from the Dmax Store is $26.00 for the 7 quarts + filter. Not a good buy. Better off going to the dealer. Tough to find Wal Mart prices on this oil.

Sounds like the plan if shipping is reasonable. Comparing prices on Amazon and Ebay, that deal is hard to beat. Mobil 1 ESP will have to wait. The local Advance Auto has the gall to sell Mobil 1 ESP 0W-30 for $12.99 a quart. They can't even get the ESP (DexosD) 0W-20. Thanks - J Tab

Hello, Getting close to 2nd oil change on my 2020 Sierra 3.0L Duramax. To make certain I purchase the correct oil, I've included a link below. The best I can determine its the Mobil 1 ESP X2 0W-20 which has the DexosD rating. Other than the AC Delco DexosD, can others confirm that this is the correct oil for the 3.0 L Duramax? It appears at this point the local auto parts stores do not stock the Mobil 1 ESP OW-20 as of yet. The link below gives the product description. Thanks - J Tab www.mobil.com/en/lubricants/for-personal-vehicles/our-products/products/mobil-1-esp-x2-0w-20/

Yes, I used the funnel supplied with the vehicle. The spout extends into the filler about 4 inches. Possible it was not long enough or I did not have it inserted far enough to by-pass the flapper. Thanks - J Tab

Need advice. Went to add some anti gel to my 2020 3.0L Duramax today. Was going to give it a 10 oz shot of additive. (Power Services Diesel Full Additive with Cetane) Inserted the funnel about 4 inches. When I poured the additive in the fuel filler it would not take the additive, ran out, and made a mess. Question - is there something restricting just inside the filler ????? Possibly I need a longer funnel ???? Thanks - J Tab

Danny, Have you measured the width of your bed at both the front and rear ? If so, what are the measurements.? I just received the BAKFlip MX4. The hard aluminum panels measure 62". The width of my 2020 Sierra Denali varies from 63-5/8" in front to 62-1/8" at the tailgate. Regards - Jaketab

Just received my BAKFlip MX4 order below for a 2020 GMC Sierra Denali 1500 series – short bed. (With multi pro tailgate) Two concerns before I completely remove the parts from the box. The inside width measurements of the truck bed vary. The front width at the rear window measures 63-5/8”. The rear width at the tailgate measures 62-1/8”. The hard tri-fold panels measure 62”. Meaning front panel is 3/4’' will be too short on each side. This may be too much overlap to fit ??? I've already sent an email to REALTRUCK and will contact them by phone tomorrow. The second concern is the bed liner is the factory stock spray on liner. The front sealing bulkhead strip most likely not stay adhered to the textured finish.

Hello, On August 5, 2020 I purchased a 2020 GMC Sierra Denali 3.0 Duramax. The truck now has 2500 miles. Except for the wheel or drivetrain balance problem, I am very satisfied with the vehicle. The fuel economy is exceptional with great power. The Sierra has a vibration problem at highway speeds on the interstate highway. The problem is a continuing vibration at 60 – 75 mph. The vibration is felt mostly in the seats. The truck has the 22” Bridgestone Alenza Tires. (275/50/R22) The problem has not been remedied through four (4) trips to the dealer. The vehicle tires and wheels have been (Road Force) balanced 3 times. One tire has been replaced and the balance/vibration continues. I suspect part of the problem may be 6 ounces or more of weight on 2 of the tires. During the most recent service visit, the service tech preformed an EVA – Electronic Vibration Analysis and test drove the truck about 25 miles. Because the vibrations (graph analysis) were within GMC specs, no further warranty repairs can be made without the consent of the district service supervisor. I had the service manager ride with me and he agreed that there was indeed a vibration as I have claimed. In the order of good customer relationship, the service manager is currently seeking approval to have new tires installed on the vehicle. As of today I am waiting to hear back from the manager. Please chime in if you have experienced this. My question to other 2019 – 2020 GMC Sierra owners is this a similar ongoing problem and what may be the solution? Could the problem be related to the drivetrain/driveshaft??? Thanks and regards Jaketab