2019 Silverado cabin rumbles when slowing down

hotrodz37 · March 10, 2020

Yes. Technically it raised the axle connection to driveshaft probably over an inch or 5 degrees. Removed .25in from front and added to the .25 to rear of the block raising the axle connection point a considerable amount. Essentially by turning the shim around it made the u joint angle almost zero. On really hard stops I can feel it slightly but I think that’s the axle nozzle rotating downward putting extreme pressure on the U joint and drive shaft transmission not wanting to downshift smoothly that causes the vibration at shift points. This all bs that makes sense in my head but I’m not a mechanic and have never replaced a u joint or drive shaft. Just happy the truck stops smooth again and I can think about other mods like rock lights and mufflers. Already got the rock lights. Lol

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Still no issues on your truck after rotating the shim? I might give that a shot when I get some free time.

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hotrodz37 · March 10, 2020

After reading a few threads, it seems as though some trucks came with shims and others didn't. Does anybody who has this issue not have shims?

Reading a drop shackle thread, those guys are getting vibration at 30mph and rotating the shim so the tapered end is toward the front of the truck seems to fix it.

STX30MAC · March 11, 2020

On 3/9/2020 at 10:22 PM, hotrodz37 said:

Still no issues on your truck after rotating the shim? I might give that a shot when I get some free time.

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Still no issues. Its worth a try. Tapered end towards the front.

hotrodz37 · March 11, 2020

Found an awesome driveline angle finder app. Going to check mine when I have a chance. Looks like our working angle should be between 1/2 and 3/4 deg.

Here is a link for the app.

https://apps.apple.com/us/app/tremec-toolbox/id858643212

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hotrodz37 · March 18, 2020

@lapoolboy - any more tinkering with your truck?

Not sure what everyone does for work but they have us working remotely now which will free up some lunch breaks to try some stuff with mine at the house.

Hopefully a few guys have made headway!

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hotrodz37 · March 26, 2020

Interesting find. The loaner I am driving right now, doesn’t have the rumble on decel. This is a 5.3l 8 speed crew cab. Checked under the leaf springs and no pinion shims. So first thing I’m going to do when I get my truck back from the dealer is remove the shims and see how it does.

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hotrodz37 · June 14, 2020

Anyone have any updates? Figured it was worth checking in from time to time.

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Stephen L. Pannell · July 19, 2020

Had it on my 2019 High Country when it was brand new. Ended up being an exhaust pipe the was touching the frame. Dealer fixed it.

Sounded and felt like driving over rumble strips. I thought it may have been the flapper valves or the torque converter or the tranny but that was not it. Get it up on a rack and look for any place the exhaust pipes may be touching any part of the frame or underbody loosen pipe clamps and adjust clearance.

hotrodz37 · August 23, 2020

Mine is fixed!!!

For anyone who is still following this. Mine was the pinion shims that came from the factory. Measured my driveline angles and the working angle from the rear end to the drive shaft was 4* difference. Shouldn’t be any greater than 1*. I Spun the shims around and it’s completely gone.

Can’t believe the dealer couldn’t figure something this simple out. Guess if you want it done right you have to do it yourself.

Not sure why the 2019’s came with shims from the factory when they weren’t needed. Seems the 2020’s don’t have shims and this problem is gone on them.

Check your angles, I bet this is your problem!

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Kenster113 · January 8, 2021

I’m having the same exact issues as most of you were having or had. I’ve got a ‘21 5.3 8spd CC Silverado. I can’t recall if mine has the shim but it would be worth trying. Had the truck at the dealer and they couldn’t find much, said they didn’t feel what I was feeling but I’m not sure why as I feel it nearly all the time, only time I don’t completely feel the rumble is if coming to a stop at slow moving speeds.

The shop foreman noted I had a muffler delete and said that could be causing a back pressure issue and it could be what’s affecting the engine and transmission. Plausible, but I did notice it when it had the muffler on.

im hoping it be the shim issue, as one other said, it does feel like a humming vibration is present when driving against a fair wind.

Edited January 8, 2021 by Kenster113

ol man · January 11, 2021

2020 silverado, double cab, 5.3L 8L90 8 speed transmission. I have a vibration issue also. It started with 4 miles on it and still does it with 11,000+. Using a "easy" foot on the brake it is not noticeable. However, if you have to be a little aggressive on the brake, coming out of high gear, the truck starts to vibrate around 40mph as you slow down, it stops 20-24mph. Lots of complaints online about this also, and yes, no help from GM or the dealer, yet...truck is there now being looked at again for the 3rd time. I drove another truck at a different dealership, same problem. The vibration can be heard and felt in the seat and steering wheel. From time to time I also get a hard shift from 1st to 2nd.

It appears the TCM is not letting the transmission downshift. However, I was hauling some material the other week which added about 500 lbs and experienced no vibration. Unloaded truck, test drove and the vibration returned. Loaded truck, test drove and no vibration. Also, it you shift into neutral, you don't get the vibration.

Consensus......the TCM is programmed to stay in a higher gear as long as possible, (fuel efficiency efforts) thus the vibration before the downshift.....add the weight and the TCM senses this and down shifts....

Depending on your transmission there is a lawsuit against GM.....the 8L90 and 8L45 are listed in the suit.

SSsierra · January 13, 2021

On 2/10/2020 at 11:10 AM, lapoolboy said:

I have the 6.2/10-speed and I DEFINITELY have the problem.

I have the 5.3 /10 speed and I also definitely have this issue, I think it is the driveline also

SSsierra · January 13, 2021

On 3/10/2020 at 12:52 PM, hotrodz37 said:

After reading a few threads, it seems as though some trucks came with shims and others didn't. Does anybody who has this issue not have shims?

Reading a drop shackle thread, those guys are getting vibration at 30mph and rotating the shim so the tapered end is toward the front of the truck seems to fix it.

I am getting this issue and I do not have the shims. I have 2020 Sierra 5.3/with 10 spd tranny

SSsierra · March 17, 2021

On 8/24/2019 at 12:10 AM, Chevy11-19 said:

I have the 5.3L V8 DFM. 8 speed transmission. The GM and Service director... Stated it may just be the characteristic of these 2019 trucks but it doesn’t mean it’s right.

On 1/5/2020 at 9:21 PM, hotrodz37 said:

Yeah I hear that, glad they took care if you with the new truck! I don’t know if it will go away or not. When I posted on here I had 150 miles and have 496 on it now and it’s still doing it.

I put it in L6 which gets rid of DFM and it still does it. I am going to put it in neutral tomorrow and see what it does. I think something is wrong with the torque converter but it’s surprising because it drives and shifts pretty flawlessy on acceleration and deceleration other than 2nd to first gear.

I would have taken it in already but I had a 2013 Sierra that spent 65 days in the shop in the first few months that I owned it and don’t want to go down that road again.

Was hoping someone on this forum might be experiencing the same and it was an easy fix haha

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I have the 5.3 with 10spd and has the same issue. I have measured the driveline angles and it is out of spec. On my 2020 Sierra they didn’t use any rear leafspring blocks or shims as they did on previous years

SSsierra · June 10, 2021

On 11/30/2019 at 12:24 PM, hotrodz37 said:

Any findings on this one? My new Denali is doing the same thing, thinking it’s the torque converter but mine has the new tranny fluid and only has 150 miles on it so hoping it will get better over time and as the transmission breaks in.

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I had exact same problem 2020 Sierra 1500 crew cab 5.3 4x4 with 10 spd. 4 trips to dealer and Dealer had no diagnostics said was operating as designed, they tried blaming the Dfm. I did tons of research which I found out it was the driveline operating angle. I had my ride height driveline angle measurements taken by a 4x4 shop trans angle was 420, drive safe was 420, rear pion angle was 0.65. I ordered a 2 degree angle shim fat end facing towards the rear and wha Leah perfect no more vibration