2019/2020 Stock Pinion Angle Shims

[hotrodz37]

Hey all,

 

I have a 2019 Denali that I have been trying to chase down a rumble in the cab when I’m decelerating from about 30-20 mph. I think it is pinion angle related or tq converter. My truck has shims under the rear leaf pack to adjust the angle from the factory.

 

There are a couple of threads about the rumble but nobody has seemed to be able to solve it. One guy did with flipping the shims but his truck was lifted so trying to figure out the protocol on a stock truck.

 

I have had a few loaner trucks and they had the very slightest rumble not anywhere near as bad as mine and the 2020’s don’t have the shims.

 

My question is, do you think GM arbitrarily added shims to 2019 trucks or did they truly measure driveline angles and put the shims on the trucks that needed it.

 

That being said, why would the 2020’s not have shims? What might have changed that they didnt need them?

 

I’m just trying to do some research before I pull the shims on my truck out which seems to be a bit involved.

 

Thanks in advance for any insight!

 

 

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[mafd2]

Try loosining the tie bolt and spinning the shim 180°.

[hotrodz37]

Try loosining the tie bolt and spinning the shim 180°.

I know spinning it has worked for you guys with lowering/level kits in the rear but my truck is completely stock.

That being said, it might be worth trying to see if it makes it better or worse instead of taking it completely out. Only problem is that swings the pinion angle like 4 degrees instead of just two by removing it.


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[mafd2]

I've ridden a '20 that had a slight vibration on decel. Try spinning shim; it's worth a try.  If it doesn't work you may have something else causing it.

[hotrodz37]

I've ridden a '20 that had a slight vibration on decel. Try spinning shim; it's worth a try.  If it doesn't work you may have something else causing it.

Agreed, I’ll give it a shot. It’s either that or the torque converter, hoping it’s as simple as the pinion angle.


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[CMillSilverado]

I have a 19' and lifted it 1.5in in the rear and 1in in the front since my High Country came almost level from factory. After I didn't like the rake so ordered a 1in block instead of the 1.5in and WOW major vibration like you have, decel from 40 or so down. It was so bad I thought I had messed up the truck. Got it back and changed out to the 1.5in and it was gone well almost gone. Now that I know what it feels like I can still feel it when I decel, it's about 95% better but I can still feel it.

 

So it seems like these things are VERY sensitive to driveline angle, I'm going to run up the street to look at an AT4 and see if the shim is in there and which way for mine. As for yours have you brought it back to the dealer?

[hotrodz37]

55 minutes ago, CMillSilverado said:

I have a 19' and lifted it 1.5in in the rear and 1in in the front since my High Country came almost level from factory. After I didn't like the rake so ordered a 1in block instead of the 1.5in and WOW major vibration like you have, decel from 40 or so down. It was so bad I thought I had messed up the truck. Got it back and changed out to the 1.5in and it was gone well almost gone. Now that I know what it feels like I can still feel it when I decel, it's about 95% better but I can still feel it.

 

So it seems like these things are VERY sensitive to driveline angle, I'm going to run up the street to look at an AT4 and see if the shim is in there and which way for mine. As for yours have you brought it back to the dealer?

 

Yeah, I think these trucks are super sensitve to driveline angle. I took mine to the dealer back in January and they had it for a week and couldn't figure it out. That being said, they didn't even mess with the shims or driveline angle, they are not very competent to say the least. All they did was tests on the transmission and reported back to GM and GM deemed it "operating as normal". They said they drove a few trucks on their lot and a few did it worse than mine and a few were better. I wouldn't want to feel the trucks that were worse than mine because mine is VERY noticeable. 

 

I think they put shims in all of the 2019's because they didn't know what they were doing. The fact my rear diff is 4 degrees off from the factory is pretty alarming. I had the rear window leak on my truck and had two 2020 loaners, same config as my truck, 8 speed trans and neither one of them had the shims and they didn't have the rumble on decel. I think that's the culprit on mine, just need to get some time to remove or spin the shims. By my calculations, removing it is better than spinning it to correct my angles. 

[Grumpy Bear]

Do you know how to use Google?

 

https://4xshaft.com/blogs/general-tech-info-articles/slopes-vs-angles

[CMillSilverado]

18 minutes ago, Grumpy Bear said:

Do you know how to use Google?

 

https://4xshaft.com/blogs/general-tech-info-articles/slopes-vs-angles

Do you even have a 19+ GM??

[Grumpy Bear]

42 minutes ago, CMillSilverado said:

Do you even have a 19+ GM??

So you think physics changed for 2019 and beyond?

Interesting idea.

Wonder if gravity will work tomorrow. 

 

 

[CMillSilverado]

Just now, Grumpy Bear said:

So you think physics changed for 2019 and beyond?

Interesting idea.

Wonder if gravity will work tomorrow. 

 

 

15' and 19' trucks are not the same, stay with what you know.

[BlancoSilverado]

18 minutes ago, CMillSilverado said:

15' and 19' trucks are not the same, stay with what you know.

Same information will apply. 

 

 

[Grumpy Bear]

2 minutes ago, CMillSilverado said:

15' and 19' trucks are not the same, stay with what you know.

News Flash

The drive shaft physics is.

 

 

 

Psssst. We are not doing this, read me?

3 minutes ago, BlancoSilverado said:

Same information will apply. 

 

 

 

[CMillSilverado]

There is something differnet, I had the same lift on my 17' and set up the driveline angle and had zero vibration, did the same to the 19' and there is vibration.

[BlancoSilverado]

On 8/6/2020 at 9:44 AM, CMillSilverado said:

There is something differnet, I had the same lift on my 17' and set up the driveline angle and had zero vibration, did the same to the 19' and there is vibration.

Did you check your angles?