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.