Jump to content

2020 Sierra 1500 AT4 Duramax Cross-Country Towing Experience/Performance review

pavementprincess20
 Share

Recommended Posts

pavementprincess20 Enthusiast

pavementprincess20

Posted
Posted

TL;DR: I drove 2,941 miles from South Florida to Southern California in my brand new Sierra 1500 AT4 Duramax and pulled my 4,400lbs pound boat. I experienced no drivetrain issues other than running out of gas which was my own fault. I kep the rpms mostly at 1500-2100, averaged 12.6 mpg, consumed 11-12 gallons of DEF and had no cooling issues under the load and in the 118F heat of the Californian desert for the prolonged time I was driving. The trailering app and trailer tire TPMS system paid for itself and was a great tool for safety! DEF gauge may not be accurate to read when towing, rather go by the mileage warnings that display on the dash. Adaptive cruise control disengaged briefly but was able to re engage after turning the truck off and back on again. I am very satisfied with the performance I experienced and overall truck and have had no issues thus far with the drivetrain (6,054 miles on the clock).

 

Hey y'all, I wanted to put some info out there about the trip I just made this week from Boca Raton, FL to San Diego, CA in my brand new 1500 AT4 Diesel to include performance numbers, issues I encountered, good, bad, and otherwise. I was a little on edge seeing as I did a decent amount of research on the new duramax before I bought it in July and there are definitely some issues out there that are yet to be addressed, however I had to move for my new job so here goes.

 

Google Maps put the trip at 2,611 miles (4,202km) from my parents driveway to my new place but my trip clock read 2,941 miles (4,733km) due to stopping in to see some family along the way. I had 3,110 miles (4,989km) on the clock before I left. Note that my backseat was full of boxes and my bed was mostly empty except a weatherproof toolbox because I don't have a tonneau cover yet and did not want my items exposed to the elements or sticky fingers for the five days I was on the road. I was also towing my boat which is a 20 foot center console on a tandem axle trailer with dual axle hydraulic surge brakes. The boat and trailer combo weighs 4,400lbs (1995 kg) as indicated by the weigh scale I stopped at in California and my WeighSafe drop hitch with tongue scale. I spent the overwhelming majority of my time at ~1500 rpm while on cruise control at 67-mph but would jump to ~2100 when gradually accelerating. 

 

I left on Sunday afternoon and drove 225 miles (362km) to Daytona Beach, FL mostly uneventful despite my DEF warning popping up saying I had a 1000 mile range. On Monday, I drove 514 miles (827km) uneventfully seeing some family and friends in the Panhandle of Florida. The only eventful part of this leg of the journey was the DEF message popping up in the morning saying I had a 300 mile range approximately 150 miles after the 1000 mile warning and a speed limited soon message shortly after the 300 mile message. I figured I would use more DEF while towing but I hadn't put much thought into exactly how much I would use while planning my trip. I will talk more about DEF later. Tuesday I drove 537 miles (864km) from Milton, FL to Houston, TX uneventfully. Somewhere around San Antonio, TX I got a message that adaptive cruise control has disengaged. I was able to switch to regular cruise control but still don't know why that happened. I was able to re engage adaptive cruise control later in the day after I turned off the truck at a fuel station. Any thoughts would be appreciated here if you have experienced something similar. Wednesday is where the fun started.

 

About halfway between Houston and Fort Stockton (508 miles, 817km) I got a low trailer tire pressure message on my dash. My truck came with 4 trailer tpms sensors I had installed into 4 new tires on the trailer about a week before I left because I figured why not. the tires are filled to 50psi as per the sticker on the trailer and the message showed front right had 35 psi. I figured all was fine and it was an error message as I had already driven over 1000 miles with no issues but I decided to stop and check at the next exit as I noticed the pressure was steadily declining. I pulled off at a Love's and went to check and could hear the air coming out but couldn't see a nail or feel the air. Regardless (after re parking in the shade at 102F outside), I took the tire off and lo and behold found a 3 inch nail in the tread near the edge of the tire. Within 15 minutes I had it plugged, refilled, reinstalled, and ready to go. That right there ladies and gentlemen justified the $85 I paid to install the sensors. Had I not known of the diminishing air pressure I surely would've had a blowout at the most inconvenient location and had to put a spare on in the heat. So that sold me on the trailer tire TPMS system, cost to install already paid for itself by saving me from having to buy a replacement tire.

 

On Thursday, the plan was to go from Fort Stockton, TX to Tucson, AZ (558 miles, 898km). I was about 30 miles away from my next planned fuel stop when my fuel level low light came on but I didn't think anything of it as I would be stopping about 20 miles before I ran out of fuel. When I pulled off at the only fuel station in the area (Akela, NM) which GasBuddy showed had diesel, I discovered much to my dismay that the station did not have a diesel pump. I knew I was probably screwed but didn't really have a choice but to shoot for Deming, NM which was 24 miles down the road. My fuel level read low so I reduced speed to improve economy and hoped for the best. Worst case scenario I run out of fuel much closer to an actual city which would reduce the time it took for a fuel delivery service to reach me. 5 miles out of Akela, a car flags me down and says something blew off my boat so I pulled over and saw that my bimini top had blown off. I figured my best course of action was to drop the boat on the side of the road and turn back and try to find it. because there was no way I'd make it to Deming after turning around with the boat. Anyways, I had to go back about 3 miles to get the bimini from the middle of the road before going back. I decided to leave the boat, get fuel, and come back for it. The boat has a tracker so I could ensure it didn't get stolen plus i had 2 tongue locks on it. I made it about 12 miles before I heard a sound from the engine that sounded like i hit debris on the road, a message popping up that said speed limited, pulled over and kept the engine idling while I inspected the truck for damage and could see none. I turned off the truck to restart it and try to get back on the highway but it wouldn't crank. I called roadside assistance from the myGMC app and a guy called me to confirm that I needed diesel and was out to me from Deming in about 20 minutes. Fueled up, started, but had a check engine light so I brought it to the Chevy dealer in Deming to get checked out and ensure there was nothing seriously wrong other than running out of fuel. It was just some computer errors from running out of fuel, had them cleared, and left for no charge. Filled my tank at the nearest fuel station, turned around got my boat, and continued on my way after a 3 hour delay and made it to Tucson just in time for happy hour!

 

Friday, I finished my trip to San Diego about 407 miles (655km) uneventfully despite temperatures reaching 118F outside. I was monitoring engine temp which was regulating well between 190 and 205 and tranny temp which kept between 185 and 203 depending on the grade. No issues at all with cooling or performance. Honestly the torque was really impressive on the 6% grade that stretched about 35 miles up and down.

 

By the time it was all said and done, i averaged 12.6mpg for the entire trip although I was getting about 14-16 after I had the bimini top stowed in the bed on the truck reducing the drag of the boat. I had to put in about 11-12 gallons of DEF throughout the trip to top off my tank at the end. I found that the DEF gauge was not displaying accurate levels because when it displayed red Low and no bars it took 4 gallons before overflowing despite the tank being about 5 gallons. The range of the DEF was not linear. It showed 300 mile range at 5 bars but dropped to red and low almost immediately after reaching that point. I learned to go by mile range not necessary gauge level and just fill up at the 300 mile range message. I am satisfied with the fuel economy i saw and was very satisfied with the performance and power available when needed thanks to the diesel. Overall very satisfied with the performance of this truck as I have had no issues with the drivetrain (knock on wood). Feel free to ask me specific questions and I will answer them as soon as I see them!

  • Like 1
DFW-AT4 Enthusiast

DFW-AT4

Posted
Posted

I also have gotten the message of "adaptive cruise control has disengaged". It has only happened once, and it was on a stretch of road where I was driving somewhat in a valley and rounded a corner that faced me directly into the setting sun. The sudden transition blinded me, so I surmised that it must had temporarily blinded the forward vision system/camera that the adaptive cruise control uses. No problems since then.

Duramax3oh Enthusiast

Duramax3oh

Posted
Posted (edited)

Fantastic read but sorry for your troubles!! Man what an eventful drive. 
 

I can also attest to your DEF findings. I just returned from a 2,400 mi trip pulling just shy of 6000 lb trailer. The DEF monitor is not a good/linear gauge to trust. I used right at 10 gallons of DEF for the trip I believe. 

Edited by Duramax3oh
  • Like 1
cltsig Enthusiast

cltsig

Posted
Posted

Enjoyed reading your thoughts around the bimini coming off and running out of gas.  I felt your pain but seems you didn't!  Enjoy the new rig.

  • Thanks 1
jojo ma Enthusiast

jojo ma

Posted
Posted

Wow, great info.  I have the 2020 3500 6.6 diesel AT4 and I live in south florida and I will be taking a trip to Utah and Colorado next year in June.  I will be towing about 10K to 14K trailer and toys.....can't wait

kpanza Enthusiast

kpanza

Posted
Posted

Great writeup!  Felt like I was a passenger...and great to hear that the Dmax Jr did so well.  My guess on the cruise control issue was some splattered bugs obscuring the sensor?  The only time it happened on my truck it was that...

pavementprincess20 Enthusiast

pavementprincess20

Posted
  • Author
Posted
On 8/16/2020 at 3:53 PM, DFW-AT4 said:

I also have gotten the message of "adaptive cruise control has disengaged". It has only happened once, and it was on a stretch of road where I was driving somewhat in a valley and rounded a corner that faced me directly into the setting sun. The sudden transition blinded me, so I surmised that it must had temporarily blinded the forward vision system/camera that the adaptive cruise control uses. No problems since then.

Sounds like exactly what happened to me because the sun was setting and very bright. Sounds like a non issue then ??

pavementprincess20 Enthusiast

pavementprincess20

Posted
  • Author
Posted
20 hours ago, jojo ma said:

Wow, great info.  I have the 2020 3500 6.6 diesel AT4 and I live in south florida and I will be taking a trip to Utah and Colorado next year in June.  I will be towing about 10K to 14K trailer and toys.....can't wait

Oh man oh man, got me a little jealous haha that should be a fun trip!

pavementprincess20 Enthusiast

pavementprincess20

Posted
  • Author
Posted
18 hours ago, kpanza said:

Great writeup!  Felt like I was a passenger...and great to hear that the Dmax Jr did so well.  My guess on the cruise control issue was some splattered bugs obscuring the sensor?  The only time it happened on my truck it was that...

Dmax  Jr ?

 

yeah seems like some sort of environmental interference versus an issue with the truck

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • Grumpy Bear
      Some Assembly is Required

      By Grumpy Bear · Posted

      Can it still be Assembled I?    Stribeck says that we need a certain amount of viscosity under conditions of load and velocity to prevent two surfaces of a know roughness from tearing each other asunder. And we have marketing trying to tell the masses that those two surfaced require less of that commodity due to more exact limits being placed on the same old clearances. We also know that there are limits to how hard something can before it becomes to brittle to be viable and to smooth to 'wet' the surface and that both of those conditions have been known and met since about the Second World War.    That viscosity value shook out at 10 centistokes at 212 F just under a hundred years ago.  Give this a look: [Anton Parr]     What is advertised is the Kinematic viscosity (mm2/s) or that which has been density adjusted but the value we are after is the dynamic viscosity (mPa.s) or true viscosity. You can see that this number is dependent on density thus base stock and temperature. You can also see that an SAE 30 doesn't reach that value in this example. However an SAE 30 that is at the upper end of the SAE 30 range; 12.5 cSt (mm2/s), might. 12.5 * .83 = 10.375 (mm2/s). If you could find an SAE 30 at the upper end these days.   Then there is the complication of viscosity modifiers or VII or VM, whatever you wish to call them. Polymers added to very thin base oils, perhaps 3 to 6 cP oils, that will meet the SAE *W30 spec at 'tested' shear rates and 100 C/212F  target temperature. So a polymer fortified base that is a fraction of the 10 cP requirement Stribeck insist upon.   This could be all well and good if those polymers didn't have two very problematic 'features'. They shear or loose viscosity both 1.) permanently and 2.) temporality. And they do both omitted in the advertised data with the distinct  purpose of deceiving the consumer of the actual operating state of the fluid. I've shown the example of Warren Oils COSTCO 10.91 cSt 5W30 formuation several times where the 100 C HTHS value is 6.9 cP!! That's the temporary shear down and with and SSI or shear stability index of 9.4 cSt. Note the intentional deception in using mixed units?    After a short while that 9.4 cSt oil has a viscosity corrected dynamic value of 7.8 cP. But as the SSI is still within the range of an SAE *W30 whose lower value is 9.3 cSt.    This allows them to continue to call this SAE 16 weight oil a 30 weight, the cake, and still meet the API requirements for fuel efficiency IMPROVEMENT mandated by the EPA. The eating of the cake. By the time you've worn out your motor doing the responsible thing by adhering to the warranty requirements, (the stick), you get deprived of the carrot, wear control. So sad, to bad.   So what can be done? Do I need actually say? [Anton Parr]       Even this must be monitored if the oil is on the low side and the VII an organic or you opt for a 0W40 with an even lighter base oil and more / higher MW VII. (Note the lower density of the 40 weight versus the SAE 30 mono-weight?)    There is another workaround. Temperature. An SAE *W30 run at a bulk temperature of between 180 and 195 F.    Being the belt and suspenders sort I am I do both. Run it cook and run it heavy.    In Part II I'll work the AW package. 
    • Atlas
      Wow I'm in a pickle. (Broke down truck) and a story.

      By Atlas · Posted

      So, do I go elbow-deep on this thing or list it for sale and play dumb? Seems to "runs good."   I'm about $1200 away from having: -a rebuilt injector ($300) -a new cat ($250) -a new cat back exhaust (OE style) ($300) -a new AC compressor ($200) -AC refrigerant charge ($150)   In theory, this should rectify the obvious detracting issues from its value and operability. Cold AC with a non-squeaking AC pulley both sounds and feels good. An exhaust that isn't cut/hacked in 17 different places and doesn't vibrate on a crossmember would make it sound and feel less janky. A working cat would help the stink, and will save the earth, but *if and only if* the fuel system is working properly, which would also address the intermittent "rich" CEL.   Heard a good one... CEL for "Rich condition" means you haven't spent enough money on the truck lately, and it's letting you know.   Rebuilding the injector would seem to be the most important part. Replacing the cat would be secondary. I don't think mine is plugged or overly restricted, but it might be a little restricted? I have no good way to tell other than seat of the pants feel. I hate the smell.   The current theory is I have a rich idle problem: A bad fuel pressure regulator, or a leaking injector(s) being the highest probabilities. I already replaced the FPR but that doesn't mean its replacement isn't also bad. It was a new part from Dorman, but the packaging looked like it had been sitting on a shelf for 20 years.   This is the (single) upstream O2 sensor shown at idle. I'm getting a lot of "rich" it seems. Sometimes it stays high like that and doesn't drop down. That makes me think it's processing injector leaks or a partially stuck open injector.     Other times it looks like this. Nice oscillations between rich and lean, which is what I think it should be. Under load and at speed, the oscillations are nice and tight and uniform looking, high and low.     Fuel trims suggest the PCM is compensating pretty hard at idle to pull fuel out. But it's not enough to trip a CEL. Something about slowing to a stop: brake vaccum booster, EGR, or the EVAP purge is delayed, or there's pooled fuel in the intake again that's draining into a cylinder is enough to set the CEL. Of course, in two days of driving, it hasn't set. I was hoping to actually look at the freeze-frame data when it sets. IAT is high because it's idling on an 83 degree day here.  
    • Another JR
      Gasser Subforum Has Been Quiet - - So, Regenerative Braking and Using L10

      By Another JR · Posted

      Have considered installing a DC to DC charger in your camper to replace your isolator?  
    • newdude
      Gas fill door

      By newdude · Posted

      Common failure.  You need to replace the fuel door housing.   The painted cover transfers over to the new housing.  To remove the old one there is 4 spots where you poke the plastic to release it.  
    • newdude
      Gasser Subforum Has Been Quiet - - So, Regenerative Braking and Using L10

      By newdude · Posted

      No such thing as regenerative braking on a pure ICE vehicle.     Regenerative braking is the re-capture of energy from electric motors and stores it in the battery pack.  So hybrids, PHEV and EVs have regenerative braking.     What you are seeing is the charging system changing modes is all.  Its likely entering charge mode for some sort of reason is all.  All of the charging modes will be listed below.   As for L10 vs D.  L10 turns off automatic grade braking.  L10 puts you in control of grade downshifts where in D it will automatically do it based on brake pedal position and other factors.  Otherwise L10 and D drive exactly the same aside from that one aspect.    Battery Sulfation Mode The BCM will enter this mode when the interpreted Generator output voltage is less than 13.2 V for 45 minutes. When this condition exists the BCM will enter Charge Mode for 2–3 minutes. The BCM will then determine which mode to enter depending on voltage requirements.   Charge Mode The BCM will enter Charge Mode when ever one of the following conditions are met:   Windshield wipers are ON for more than 3 s. Climate Control Voltage Boost Mode Request is true, as sensed by the HVAC control module via serial data. High speed cooling fan, rear defogger, and HVAC high speed blower operation can cause the BCM to enter the Charge Mode. The estimated battery temperature is less than 0°C (32°F). Battery State of Charge is less than 80%. Vehicle speed is greater than 145 km/h (90 mph) A current sensor malfunction exists. System voltage is determined to be below 12.56 V When any one of these conditions is met, the system will set targeted generator output voltage to a charging voltage between 13.9–15.5 V, depending on the battery state of charge and estimated battery temperature.   Fuel Economy Mode The BCM will enter Fuel Economy Mode when the estimated battery temperature is at least 0°C (32°F) but less than or equal to 80°C (176°F), the calculated battery current is less than 15 A and greater than −8 A, and the battery state-of-charge is greater than or equal to 80%. Its targeted generator output voltage is the open circuit voltage of the battery and can be between 12.5–13.1 V. When fuel economy mode is active, the generator is not charging, only maintaining open circuit battery voltage. The BCM will exit this mode and enter Charge Mode when any of the conditions described above are present.   Headlamp Mode The BCM will enter Headlamp Mode when ever the head lamps are ON (high or low beams). Voltage will be regulated between 13.9–14.5 V.   Start Up Mode When the engine is started the BCM sets a targeted generator output voltage of 14.5 V for 30 s.   Tow/Haul Mode (if applicable) Pressing the Tow/Haul Mode button located on the center stack, the vehicle system voltage is raised and the remote (non-vehicle) battery will be charged. Having the headlamps on will raise the system voltage and if the Tow/Haul button is applied it will not serve any purpose. The voltage is regulated between 13.9-14.5 V.      

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...