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Just to clear the air guys anybody who has driven a Duramax is familiar with the intermittent ticking noise. The noise that some, not all of the 2020 Duramax’s have is definitely not the same ticking noise but a definite knocking. If your driving a 2020 L5P and it is not making the knocking noise (and you would recognize it if it was) then your one of the lucky ones. My 2020 Sierra SLT 2500HD has 7900km on it and has been in the shop since last week where they are repairing the injectors in a hope of correcting the problem. Hope this helps clear up any confusion between the familiar ticking problem and the current issue with the knocking in the 2020 Duramax
 

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I'll just throw this out there. I hope the 20's tow better than the 19's.

Any explanation? I've had upwards of 16,000 lbs behind mine and haven't noticed any issue.
 

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I've had a 2004.5 LLY, 2007 LMM, 2017 L5P, and now this 2020, and I have to say, it's the nicest one out of them all. To those thinking of getting one, or hesitant, go for it. You only live once.
 

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I have had my 3500 Denali crew cab long bed dully for about one month now. My truck came with the 4 trailer tire sensors ($50) option, Michelin A/T tires ($200) option, high idle and some other stuff. Compared to my 2008 LMM this is the smoothest riding truck I have ever owned (the bumps are firm not bouncy). The steering is light and feels like my Honda Accord's steering. The truck is very quiet inside compared to my LMM which vibrated the dash at idle. The tail gate is a must. The truck is so tall it would be hard for me to get in and out of the bed without it. I think the L5P is so quite that you now hear sounds my LMM would cover up. I hear the fan more then the engine. I like all of the sounds she makes. If I wanted a quite truck I would have got one with a gas engine.

At 456 miles on her ticker the oil is not that dirty. My LMM was black as soon as I started her up. The transmission has no dip stick so I can't check the fluid or smell it to see if it is burned.

Every time I found a Chevy or GMC dully I liked on the internet they sold it before I could get to the dealer. There are a lot of single rear wheel but not dullys where I live.
 

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I have had my 3500 Denali crew cab long bed dully for about one month now. My truck came with the 4 trailer tire sensors ($50) option, Michelin A/T tires ($200) option, high idle and some other stuff. Compared to my 2008 LMM this is the smoothest riding truck I have ever owned (the bumps are firm not bouncy). The steering is light and feels like my Honda Accord's steering. The truck is very quiet inside compared to my LMM which vibrated the dash at idle. The tail gate is a must. The truck is so tall it would be hard for me to get in and out of the bed without it. I think the L5P is so quite that you now hear sounds my LMM would cover up. I hear the fan more then the engine. I like all of the sounds she makes. If I wanted a quite truck I would have got one with a gas engine.

At 456 miles on her ticker the oil is not that dirty. My LMM was black as soon as I started her up. The transmission has no dip stick so I can't check the fluid or smell it to see if it is burned.

Every time I found a Chevy or GMC dully I liked on the internet they sold it before I could get to the dealer. There are a lot of single rear wheel but not dullys where I live.
Is your truck making the thumping or knocking at idle that some of us with the 2020 L5P are experiencing?
 

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A small thumping sound at idle but not that bad. The fan makes the most noise. But like I said in my other post, she is not as noisy as my LMM was. She is still the best truck I have ever owned.
 

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A small thumping sound at idle but not that bad. The fan makes the most noise. But like I said in my other post, she is not as noisy as my LMM was. She is still the best truck I have ever owned.
I agree my 2020 Sierra is a great truck however beware mine now has 19,000km (12,000 miles) on it and the thumping has worsened to the point that anybody that hears the engine at idle asks what’s wrong with it. How will this affect the sale of the vehicle when the time comes? GM knows that some, not all, of the 2020 L5P Duramax engines have a problem, they have narrowed it down to the fan clutch why not recall the affected vehicles and fix the problem.
 

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, they have narrowed it down to the fan clutch why not recall the affected vehicles and fix the problem.
Because GM is working to fix issues that affect performance.
The thumping noise does not affect the performance of the L5P motor at this time.
Giving the issue some time will:
A. Let the engineers thoroughly research and study the issue.
B. allows the issue to develop over time to see if it eventually affects performance with age/mileage.
The more that report the issue the more attention it will get and in time the issue will be resolved.

(y)
 

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Because GM is working to fix issues that affect performance.
The thumping noise does not affect the performance of the L5P motor at this time.
Giving the issue some time will:
A. Let the engineers thoroughly research and study the issue.
B. allows the issue to develop over time to see if it eventually affects performance with age/mileage.
The more that report the issue the more attention it will get and in time the issue will be resolved.

(y)
I agree we need to keep reminding GM of the issue as the Dealership advised recently that they cannot get any response from GM on the matter. However one would think that if GM were prepared to acknowledge that they have a problem and are working to resolve it that they would simply let current owners know
 

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Good day, signed up to post my review, hope to stick around.
2020 High Country factory built, left out the sunroof, offroad package, and dual alternators. Waited 7 months for it to come, longer wait then I expected.

It replaced a 2016 Ram 3500 SRW Laramie that I put 194k km's, 2/3 with a trailer behind it.

I put on my 1200 km non towing as per the manual, then hooked up the trailer, 20+8ft gooseneck cargo a little over a week ago now at 2900 km trailer will stay on the truck for awhile.

My first impressions honestly are not great, I am looking at replacements as my main rig and will delegate this as backup.

What I like, start there.
1. Hud, it works well, while I would like more info, but with just the speed and limit it works well.
2. It gets going and moves well and shifts beautifully. I had the Aisin in the ram and this 10 speed is smooth and predictable. It keep a cruise speed while my trailer is on, shifts quick and keeps the set speed.
3. Mirrors, while some hate them I love being able to switch to towing while in the cab and not have a bunch of adjustments to make after switching.

What they got wrong.
1. Aux switches, I order factory installed for a reason, finding the wires loose after taking possession and the instructions saying this is my problem is not exactly something that sits well.
2. Exhaust brake, well it sucks, I own a few commercial trucks, you pull your foot off the accelerator the exhaust brake kicks in, transmission downshift. You can typically get down to 40 km/h without touching the brakes, my 2020 high country it only activates going downhill with tow/haul mode activated. I got 170k km's on my ram brakes as you learn to use the exhaust brake to control things.
3. Camera connections on the bumper don't exactly work for a gooseneck and I have been hearing guys have been sheering the connectors off trying to make it work. I didn't get a camera with the truck and will avoid going that route now. Also to put the camera connections on the bumper they eliminated the 4 pin connector that I would have used if I pulled my boat. That connector is in the bed, I would neec an adapter to use the bumper, not a $100k truck mistake that should have been made.
4. I am hoping they can fix this, but I doubt it. Truck turned off, unlocked, trailer theft turned off, trailer detection turned off, trailer lights flash every 10 seconds while connected. Some think its security, but everything is turned off. I am sick of unplugging the truck every night, also if I had employees that forgot to plug it back in and had a 15k lb trailer without lights or brakes.
5. I stop and start the truck multiple times during the day. 7 out of 10 times the truck can't remember the trailer and goes to guest trailer. 9 out of 10 times it can't remember the gain set and I have to go check and adjust. My trailer weight fluctuates between 8k to 16k lbs during the day. I adjust the gain as needed, but I have to always double check. I just want the controller to stay on the last trailer with the previous gain. Trailer detection is off, but on made no difference. Hoping the dealer can fix this.
6. Def usage and or capacity. First 1200 km's were highway km's no trailer, different speeds, next 1600 km's trailer stayed on, i have 300 km's left of fluid. I am guessing next tank keeping the trailer on will be less then 2500 km's per tank of def. I fill the truck with a slip tank, def filling is a pain to do as i have to essentially do it every 1.5 weeks, i got 4-5 with my ram. Hoping this solves itself, but not acceptable in my books.
7. 12000 km oil changes are half of what I got on my Ram. With synthetic oil and a proper filter we should be able to do the same. Its the time and costs, this is my main unit, any time I spend working on this is time I essentially don't get to spend with my 3 young kids.

If things are fixed by the dealer I will update, truck is used daily though, It has work 7 days a week atm.
 

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I ordered a 2020 GMC Sierra 2500HD Denali Duramax diesel crew cab 4WD and I have only driven less than 500 miles. I really like almost everything about the new truck except the increased DEF consumption and the comfort of the ride when unloaded. It is the sharp, jolting ride on rough roads that is really annoying. I know some of you lower your tire pressures when not towing a significant load. How do you then defeat the Tire Pressure Monitoring System that sounds the horn at various times? Is there any aftermarket suspension equipment that will soften the ride when unloaded. I have been told that airbags are not the answer. What else would you recommend?
 

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dealer can reprogram the tpms. i get mine set at 55. get used to the ride its a HD 2500 with 10 ply tires.
 

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I've been away from the forum and from Duramax ownership for quite a while until I recently bought a 2020 GMC Sierra AT4 2500HD. I absolutely love the 2020 HD's and have no complaints with mine yet whatsoever. It was manufactured in February and I've got about 1500 miles on it so far. We haven't been able to pull our 5th wheel yet other than a test run around town after I got the new puck style hitch purchased and assembled but plan to take it out on a trip Friday. I'll share our trip towing experience when we return. Our 5th wheel is a light weight at about or under 10K lbs loaded so it won't be much of a pull for the new truck.
635271
 

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I've been away from the forum and from Duramax ownership for quite a while until I recently bought a 2020 GMC Sierra AT4 2500HD. I absolutely love the 2020 HD's and have no complaints with mine yet whatsoever. It was manufactured in February and I've got about 1500 miles on it so far. We haven't been able to pull our 5th wheel yet other than a test run around town after I got the new puck style hitch purchased and assembled but plan to take it out on a trip Friday. I'll share our trip towing experience when we return. Our 5th wheel is a light weight at about or under 10K lbs loaded so it won't be much of a pull for the new truck.
View attachment 635271
Please do post you impressions. We are going down this route in the next few years. That's why I am on this board ow. Trying to learn as much as I can before "pulling the trigger" on a 2500. After looking at many 5th wheels we have decided to keep the weight somewhere around 12,000 pounds or so.
 

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I recently bought a 2020 2500 CCLB GMC. Previous truck was a 2004 LLY DMAX. New truck is incredible. Towing performance is amazing. The 10 speed kicks ass. Only have 1500mi on it so far but no problems yet. DEF gauge works fine. So far really happy with it. Scared of future emission problems that may happen out of warranty but have a long time before needing to worry about that.

The quietness is just amazing. Road noise and engine is so much reduced. Easy to speed because you think your going slower by the noise.
 

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I did rely on Google and here is the result:

The Sierra is a fine truck, and its reasonable starting price makes it a decent value. However, it sits in the middle of our rankings because it can't quite match the all-around excellence of some competitors. With that in mind, before buying the Sierra, you should see how it stacks up against rivals like the Ford F-150 and Ram 1500. You could also compare it to the Chevrolet Silverado, but that really won't tell you much, as these two GM trucks are essentially twins.
 

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I did rely on Google and here is the result:

The Sierra is a fine truck, and its reasonable starting price makes it a decent value. However, it sits in the middle of our rankings because it can't quite match the all-around excellence of some competitors. With that in mind, before buying the Sierra, you should see how it stacks up against rivals like the Ford F-150 and Ram 1500. You could also compare it to the Chevrolet Silverado, but that really won't tell you much, as these two GM trucks are essentially twins.

So your going to base your truck purchase on what someone writes in a mag or on the internet about a F150 or 1500 that does not have a L5P Duramax engine. I test drove a F450, F350, Ram 3500 and GMC 3500. The GMC was the best truck I drove. The difference between a Chevy and GMC are the trim lines.
 
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