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General Motors created a buzz when they released a small block inline 6 3.0-liter Duramax diesel for a variety of trucks and SUVs like the 2020 Chevy Silverado 1500 and newly updated 2021 Chevy Tahoe. However, there is a big detail prospective buyers need to know about this engine.

Officially, this engine is also found in the 2020 GMC Sierra 1500, 2021 GMC Yukon and 2021 Chevy Suburban. Although, it is absent in both the off-road versions of GM’s full-size SUVs (more on that in another story).

3.0L Duramax Turbo-Diesel Engine

3.0L Duramax Turbo-Diesel Engine

The engine is a ground up design made to fit perfectly in those vehicles and produces 277 horsepower and 460 pound-feet of torque in the half-ton Silverado with a surprising peak torque at just 1,500 RPMs.

It also includes a variety of innovative engine technologies like ceramic glow plugs that heat up faster providing a quicker cold start, a lightweight aluminum block, low pressure EGR and a variable geometry turbocharger.

That’s a lot of fancy words to say the inherently balanced inline-6 is the leading edge of new diesel engine technology. However, there is that one thing.

What is that one thing? As soon as the news of the engine hit the internet, people quickly pointed to an oil pump belt residing in oil and needing to be inspected at 150,000 miles. While the belt sitting in oil is a bit concerning to many, the fact it is a belt, not a chain or gear driven, also drew some concern. Yet, the MOST concerning part of the belt is the fact you have to drop the transmission to service the belt. Yes, that’s not a typo. You have to drop the transmission to be able to access the belt to INSPECT it at 150,000 miles. This has drawn a lot of criticism.

We received so much feedback on this concern, we reached out to GM to interview their engineer on this engine. This engineer has been with this engine since its creation and spoke to us at length about why the belt was chosen and why, yes, it is true, the transmission has to be removed to access the belt.

Check out our video interview below:

The bottom line

While yes, removing the transmission to inspect a belt is rather ridiculous, and you are looking at around $1,000 for a mechanic to do the inspection, we are talking about a one-time inspection at 150,000 miles. We agree, we don’t like it anymore than you do, but the driving experience from the diesel outweighs the hassle in our opinion. Plus, the fuel economy in the Silverado 1500 approaching an unheard of 30 MPGs is crazy good.

GM tells us they are looking closer at this belt and will be seeing what they can do to redesign or change out the belt for something else. If they do, we will let you know. For now, just be aware as you are shopping what you are getting into.

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Tim Esterdahl

Automotive Journalist Tim Esterdahl has been a lover of trucks and SUVs for years. He has covered the industry since 2011 and has pieces in many national magazines and newspapers. In his spare time, he is often found tinkering on his '62 C10 pickup, playing golf, going hunting and hanging out with his wife and kids in Nebraska.

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45 Comments

  1. Brandon August 3, 2020

    Tim I think I know how you can figure out if this is a big problem or not. Next time you get one of these as a press loan, just drop the transmission and replace the belt in your driveway. Shouldn’t take long, just a few cases of beer to get that job done lol!

    Reply
    1. Tim Esterdahl August 4, 2020

      LOL. That is NOT going to happen.

      Reply
    2. Howard December 27, 2020

      The engineer speaks of packaging constraints for the oil pump and belt. Why not position the pump up front and have it driven with the other accessories. So the belt and pump can be easily inspected and changed.

      Reply
      1. mstangt February 18, 2021

        There’s a world of difference between an external oil pump driven by a dry belt, and an internal oil pump driven by a wet belt. Even an internal oil pump at the front of the engine wouldn’t be much more accessible than it is at the back, depending on the design of the truck. If a front mounted oil pump requires removing all the belt driven accessories, radiators, oil pan, timing cover, and other components, I would GLADLY opt for just dropping sliding the transmission back and removing a cover panel to access it.

        At any rate, changing a belt at 150k miles is about the same service interval as most timing chains on modern DOHC engines. Go ask Toyota how much they want for changing the timing chains, guides, and other associated components on a Tundra’s 5.7L V8 (180k to 200k is a normal mileage for this service). I bet it’s around $2500, if not more.

        Reply
  2. Eric September 30, 2020

    Actually, it’s not a timing belt. It looks like a timing belt, but it’s the oil pump belt. No one seems to blink at replacing timing belts at 80-100k miles in most cars (at a $1000), but they lose their minds if you have to inspect (or replace) a belt at 150k miles.
    If you want to throw stones, hurl one at the overly-complicated Active Thermal Management system with its temperamental rotary coolant valve. LOTS of complaints/repairs reported. Owners say the system goes haywire and puts the vehicle in limp mode. Expect a push for a recall.
    I think the Duramax 3.0L is a great counter-attack in the war on diesels in America. Just needs to bake a little longer.

    Reply
    1. Tim Esterdahl October 1, 2020

      Thanks, I updated the post. I meant to say oil pump belt, but had timing belt on the brain.

      Reply
  3. Neil Miles October 10, 2020

    Someone mentioned and loosely compared changing a timing belt at 80 to 100 thousands miles under the regular maintenance schedule to the dynamax change out of the oil belt. This comparison it like discussing apples vs. Alligators. Remember, many timing belts can be done by owners while the new dynamax requires a drop of a transmission Anyone who is stupid enough to think you will get a dealership to do the replacement for just $1000 hasn’t been to the dealerships around our areas or else you are on a different planet than the rest of us. After speaking to our local Chevy and GMC dealership guys they give a more realistic cost of between 12 and 16 hundred dollars. In my book this by itself is a No Buy reason. It’s not the engine or its wonderful numbers , but the idiot who made the decision to put a belt on instead of a heavy duty chain should be shot.I can hear the engineer now saying ” Hey it’s at 150,000 that’s 8 to 10 years down the road, and when the belt breaks and it will, when they hear what it’s going to cost to repair it we’ll just get a new sale everytime, buyers are so dumb”

    Reply
    1. Ryan October 23, 2020

      it wasn’t the engineer who said this, it was the suits.

      Reply
      1. Howard December 27, 2020

        Too bad it hasn’t kept the price of the truck down.

        Reply
    2. Shane Grogan January 17, 2021

      The engineer that made the decision was interviewed and gave an explanation. The reason was due to packaging . They would not have been able to fit the inline 6 cylinder in the vehicle with all the extra components needed for a chain drive. There are also a couple of other important notes.

      1.) the belt is designed to last at least 150k miles. In testing the belt did not break well over 150k miles and they didn’t have a belt break in any of their testing. The bottom part of the belt is sitting in oil, therefore it will not crack or get brittle with age.

      2.) The cost of labor would have been more putting the belt on the front of the engine (disassembly of the entire front of the vehicle to access it is more labor than dropping the transmission).

      3.) The belt doesn’t even need to be serviced as a maintenance item. If the belt breaks there is no catastrophic engine damage. An oil pressure warning would be immediately displayed giving you time to pull over, shut the engine off and call for a tow.

      Reply
  4. Kaze October 12, 2020

    Don’t know if this is related to the oil belt, but this is my 2020 Silverado 1500 3.0L Duramax after just 5900 miles. https://youtu.be/AX-KAzU90ww Started a trip and within 15 minutes began feeling a vibration. Eventually got worse to what you see in the video. Exited the freeway and the description will tell the rest, but the engine seemed to have seized with no warnings. Been told GM is replacing the engine, but haven’t said what the issue was. Two interesting things from this we’re not warning lights or gauges indicated there was an issue with the engine (thought initially a tire had blown), second after dropping the truck off at the dealership, I later found out a second truck was there with similar symptoms. A little bit concerning for this new engine. If anyone has some ideas, wouldn’t mind hearing them.

    Reply
  5. Ryan October 23, 2020

    No one has touched on the fact that this diesel engine has an aluminum engine block with Iron Liners! Iron Liners in an Aluminum Block probably not a good idea!?? any thoughts on this? I.e. difference in thermal coefficiants between different metals? Just Scary!

    Reply
    1. bob December 10, 2020

      are you an ideate ? NHRA motors have been doing that for years

      Reply
      1. Brian in Az January 21, 2021

        If you are going to insult someone, you should at least check your spelling. Otherwise, we will all know they YOU ARE THE IDIOT! :O
        NHRA motors are aluminum, yes, BUT they are rebuilt after EVERY 60 seconds of run time. Not a good example of durability.
        Aluminum blocks flex too much to be used for Diesel engines in my opinion.

        Reply
    2. Steve in Seattle December 15, 2020

      No, Nearly every aluminum V8 in existence used iron sleeves for decades.
      – Iron block, cast iron pistons, cast iron heads, car iron intake
      – Iron block, cast aluminum pistons, cast iron heads, cast iron intake
      – iron block, sintered powder aluminum pistons, cast aluminum heads, cast aluminum intake
      – aluminum block w/iron sleeves, forged aluminum pistons, cast aluminum heads, composite intake.

      Cast iron sleeves, especially Siamesed ones that install as one single bank, are very reliable.

      Reply
      1. Brian in Az January 21, 2021

        Those were gasoline powered units. Diesel is a different animal all together.
        Unfortunately, the US automakers are slow to learn and late to the game.
        I have Sprinters with the 3.0L diesel for work vehicles and they are years ahead. Audi had inline 5 cylinder diesels decades ago; 1978. GM could have used that 25 years ago and been ahead of the game.

        Reply
      2. Marvin L McConoughey February 10, 2021

        Concur. The technical issues involved should be well understood by any modern car or truck company.

        Reply
    3. Brian in Az January 21, 2021

      Just a repeat from their first experience with aluminum gas engine blocks….
      Run, do not walk from this engine to your nearest Ford or Dodge Ram dealer……

      Reply
    4. Marvin L McConoughey February 10, 2021

      The choice of aluminum for the engine block is not, by itself, fully informative. Much depends on the detailed engineering applied, the quality of the metallurgy, and how much material was used to gain strength. One hopes that GM has done well because owners deserve reliability in their costly vehicles.

      Reply
  6. Ryan October 23, 2020

    so anyone want to comment on the Iron liners in an aluminum block?

    Reply
    1. Ryan October 23, 2020

      why do you keep pulling my comments?

      Reply
      1. Tim Esterdahl October 26, 2020

        Hey Ryan,

        Not pulling your comments. They just got caught in a filter we have been using. I’ll adjust the settings. Thanks.

        Reply
        1. bob December 10, 2020

          you can pull his comments his a d…a..

          Reply
          1. Howard December 29, 2020

            The packaging issues the engineer talks about sounds week this is a truck and a couple of more inches out front shouldn’t make a big difference. After all the current model was made with this engine in mind so they say.

            Reply
  7. Jared Harris November 1, 2020

    I own the GMC duramax 3.0l and absolutely love it first diesel I’ve owned. So far no foul almost 3k miles and she is stronger then the day I brought her home.

    Reply
    1. Terry February 18, 2021

      Do you have any issues using oil?

      Reply
  8. Jared Harris November 1, 2020

    Seems my posts don’t make it either.

    Reply
    1. Tim Esterdahl November 3, 2020

      Your posts are here. Thanks for commenting!

      Reply
  9. Richard Williamson November 22, 2020

    Any info on aftermarket upgrades for the diesel? Exhaust or turbo…
    Same goes for the turbo 4 cyl.

    Reply
    1. Tim Esterdahl November 23, 2020

      I haven’t heard of anything.

      Reply
  10. Enrique Garcia November 25, 2020

    even $1200 to $1600 to drop the transmission and check the oil pump belt and replace is more like $2500 or $3000 dllrs

    Reply
  11. Rob S November 29, 2020

    I’m looking to purchase a 2022. The Silverado 1500 with 3.0L Duramax is on my option list. Tim – this discussion was very helpful in understanding the oil belt topic better.

    But I will say – another huge issue is the interior design. If the reviews are – the Silverado 1500 interior design is better (how can it not be) but still far behind the competition – I’m done waiting. I suspect we will see tow limits go above 10k for the 3.0L too.

    Reply
    1. Tim Esterdahl November 30, 2020

      Yeah, the interior leaves a lot to be desired.

      Reply
  12. Tim Warner December 12, 2020

    Now I’m all afraid because of the video of the guys try k vibrating and engine seizing

    Reply
  13. David Kaercher December 24, 2020

    Gentlemen, I own a 2020 GMC AT4 with the new 3.0 Diesel. I love the truck, but the engine — at least for me — is a dog. As I write this, it is sitting in a shop in Slidell, LA following a trip to see my family. Here I sit, with no transportation from a truck with less than 10,000 miles on it. This is the 4th visit to the dealer in the past 6 months for “Decreased Engine Power” error message and “service engine” light illuminated. So far, 14-days off the road from summer to now. The decreased engine issue really inhibits driving and it is meant to protect the engine from something two different GMC dealers 1,000 miles apart cannot figure out. So, here I sit at Christmas with no truck to play Santa with. Now I’m getting angry and I’m turning up the Social Media heat on GMC to fix this or take the darn truck back. BTW, this is the 7th GM product I have owned and my wife drives a Suburban. Thanks for letting me vent. Merry Christmas!

    Reply
  14. Steve December 26, 2020

    Well, as European but fan of American trucks, I am amazed Americans finally discover “saving fuel” issue and discover that a 3 liter TD might work as well like in the millions of mid-size trucks worldwide. Well, technology helps and the power smaller diesel engines produce are beyond what Mr. Diesel would ever dream of. I am also surprised GM chose inline-6, that’s a bit older fashioned, but inline-6’s are known since over 40 or more years for great torque and smoother running (BMW got stuck with them for very long for that reason, Jeep had the venerable 4.2 and 4.0s). Problem is the length of the engine, and think GM tried to have a trick around this with the oil belt, quite special. They might try a know-off 4-cylinder for the smaller cars. Just to say, I own a 6.5TD Suburban, old fashioned, and well, V8 is my hobby, but daily driver it is no more. So my headache will be, choose love or mind for the next generation vehicle haha.

    Reply
    1. Howard December 27, 2020

      The packaging issues the engineer talks about sounds week this is a truck and a couple of more inches out front shouldn’t make a big difference. After all the current model was made with this engine in mind so they say.

      Reply
      1. Brian in Az January 21, 2021

        A couple inches longer out front equals hundreds more per unit in costs. They try to reuse the frame, doors, beds, etc from previous models. Lengthening the truck’s nose/hood would require redesign and proportioning of the entire truck with significant costs.

        Reply
  15. Byron January 30, 2021

    “You have to drop the transmission to be able to access the belt to INSPECT it at 150,000 miles. This has drawn a lot of criticism.”. Respectable journalism is a thing of the past. You can’t just quote the engineer directly and say “replacement schedule is 150k miles”?…. How pathetic is that? Definitely not subscribing.

    Reply
  16. SteveG4 January 30, 2021

    This new GM “light-duty” diesel does look interesting. There’s unique new technology integrated into this diesel, therefore I will wait two or three years to see if GM fixes its issues, or even keeps it within their engine lineup.

    One nit-pick so far… this new “Dexos-D” 0W-20 oil! Really? A 20 weight oil in a diesel? Does GM want the engine to last, or only through the warranty period? I’m thinking Shell Rotella T6 0W-40 or 5W-40 will be its prescription before long.

    Reply
    1. Mike Sorge June 3, 2021

      All about fuel economy. That’s the big push on this engine. Longevity is earned over the test of time. I’m betting this won’t be any better then the run of the mill gas engine and nowhere near the longevity of a proper diesel.

      Reply
  17. Jake March 4, 2021

    I’ve waited for 12 years for GM to resume diesel Suburban production. My 96 K2500 Suburban with the 6.5 was a great vehicle. The V-8 grunt was well worth the smoke and noise.

    I now drive a 6.6 Liter Duramax Suburban (conversion). The horsepower and torque are so much better than anything available in a current pickup or SUV. Yes, it’s tuned and running strong. I just can’t see myself trading the big Duramax for the six-banger. It seems like a huge step backwards. Despite all that, I may test drive one to confirm my suspicions.

    Reply
  18. Keith March 7, 2021

    Assuming the tranny lasts 150K miles, I would just pull it, replace the diesel motor belt, and install new / rebuilt tranny. None of my 3, Chevy 1500 trannies have lasted 150k miles, so the belt will likely be replaced about 125k miles, when the original tranny is being replaced. I don’t see the problem unless you think the new 10 speed tranny should last 200k miles.

    Reply
    1. Mark March 22, 2021

      It will if you actually service it. If you believe the ‘150k service interval’ for the trans fluid it won’t. Speaking from lots of personal experience, albeit with older transmissions (would have to be to put over 200k on them)

      Reply
  19. Hans Eide April 1, 2021

    I hate to quote Murphy’s  law, but when you make something inaccessible it usually

    fails.
    The timing chain could be the problem being inaccessible, Audi tried this.

    But don’t worry with the 20wt oil the engine won’t last 100k so it won’t be a problem.

    Tundra’s don’t need the timing belt changed, the water pump fails between 180k to 220k
    the belt lasts 300k but it isn’t submerged in oil. Has anyone run a belt submerged in
    oil before?

    Just a stupid Mechanic 

    Hans

    Reply

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