2020 3.0 Duramax motor mount issue

gwm71 · May 3, 2023

Hello, new member first post.

I have a 2020 LT 1500 with the 3.0 Duramax and I have about 65k miles on it.

I've had nearly zero issues since new, but developed a clunk when accelerating after shifting from reverse to drive (not u-joint clunk).

Anyway, dealer diagnosed both motor mounts failed and replaced under warranty.

My problem started after this, very harsh idle vibration that rattles everything in the truck. Upon returning to have this addressed, I was informed that the truck originally had a solenoid to make the motor mount variable (softer at idle), but was deleted and standard mounts are now used to replace these.

Anyone else ran into this issue?

Georgevu · April 25, 2024

I just started dealing with issue yesterday April 23rd. Not sure what they’re going to do but I was given the same answers you were given. This can’t be the way gm will handle this problem.

Georgevu · April 25, 2024

What ended up happening with your truck?

Gsolis · October 10, 2024

The same problem is happening to me!!!! Any new infor on this?

Dan House · March 5

I have a 2020 high country. Same thing happened to me. Rattles like a 1960s truck with 100k miles, except mine cost alot more!

Has GM come up with a solution to this design flaw?

GMCustomerService · March 5

9 hours ago, Dan House said:

I have a 2020 high country. Same thing happened to me. Rattles like a 1960s truck with 100k miles, except mine cost alot more!

Has GM come up with a solution to this design flaw?

We would like to get to the bottom of this rattle. Please send our team an email to [email protected] with your VIN, mileage, and your preferred dealerships name. Please be sure to include "GMC Trucks Forum" and your username in your email. By sending us a message, you consent to the information you provide being monitored and recorded by GM or those acting on GM’s behalf, subject to the GM Privacy Statement: https://www.gm.com/privacy-statement.

ChevyRST · March 16

I just changed mine myself, and the same thing is happening with mine. Whatever that was changed with all the revisions with these motor mounts, they were not constructed well. I changed the passenger side on my 2020 Silverado 1500 LM2 3.0 with 75,000 miles, and the vibration that it is now making is crazy.

ChevyRST · March 16

On 3/5/2025 at 8:40 AM, Dan House said:

I have a 2020 high country. Same thing happened to me. Rattles like a 1960s truck with 100k miles, except mine cost alot more!

Has GM come up with a solution to this design flaw?

Can you post if you come across a solution? I have a 2WD, and I installed part # 11549180. There is another mount that is supposed to be for the 4WD (85623482), which I ordered. It should be here towards the end of the week. I am hoping it is constructed differently and that it will fix it. Can you see your invoice and post which part # you had installed on your truck?

ChevyRST · March 24

I found the issue that was causing the terrible vibration and a resolution.

Transient · March 28

On 3/24/2025 at 5:16 PM, ChevyRST said:

I found the issue that was causing the terrible vibration and a resolution.

And...?

ChevyRST · April 5

On 3/28/2025 at 12:02 AM, Transient said:

And...?

2020 Silverado Engine mount

I changed my passenger-side motor mount about two weeks ago and had the same issue that was reported by multiple people on this forum: www.gm-trucks.com/forum. I will get back to this in a few minutes.

The Approach:

I ended up doing a wheel well (side) approach. It worked out well. There were a lot of interruptions throughout the day, so it was difficult to gauge exactly how much time I spent on this project. I believe it was approximately 6 hours, but it can definitely be reduced if I were to do it again to 4-5 hours or maybe even less. I will be putting a video together and posting it to YouTube.

The aftermath of changing the engine mount: Terrible vibration

There was a really bad vibration after changing the passenger motor mount. The best way that I can describe it is if you are sitting in a vehicle with a gas engine that has a bad coil. According to this forum https://www.gm-trucks.com/forums and other forums, it seems like others have had this same result, even when getting the mount replaced at the dealership. Dealerships blamed the issue on the revised mounts.

Diagnostics process and discovery:

After almost 2 weeks and about 10 hours worth of troubleshooting, I discovered the issue. I found that even though the vibration was an "intense vibration," it was greater on the driver's side. I theorized that I may have damaged the driver motor mount when I raised the engine since they are hydraulic mounts, oil-filled, and have a shaft. I replaced the mount on the driver side, which I found leaky anyway, but the vibration worsened instead of getting better (new mount = stiffer mount = more vibration). One thing I found when replacing the driver-side mount is that the alignment of the mount, the bracket that holds it in place, and the alignment to the frame did not align as smoothly as the passenger mount. I loosed the bolts on the passenger mount and the vibration remained the same; I loosed the bolds on the driver side and the vibration resolved. The next theory was based on the strong vibration on the driver's side, the misaligned motor mount, and the resolution of the vibration when I loosed the bolts on the driver's. I figured, there was one other part between the engine block and the frame other than the engine mount which was the engine mount bracket that is between the motor mount to the engine block. After replacing the engine block mount, it went back to being as smooth as when I drove it off the lot. What I discovered when I compared the old mount vs the new mount was that GM updated the motor mount bracket that holds the motor mount to the engine block. The bracket is thinner and has a slightly different angle/pitch. Replacing the mount on the driver's side can be done in approx 1.5 - 2 hours.

Recommendation from me to you:

When you replace the motor mount, don't just replace one, replace both driver and passenger mounts; replace the engine mount brackets on both sides as well.