2020 4WD Denali lowering shackle issues

tuckin22 · June 28, 2020

Just decided to put a lowering shackle on the truck as it has been getting decent comments aside from the shims needing flipped and sure enough have the same issue with vibrations.
Dropped it the full 2”.

Here is my problem. I have no shim on pass side and driver side looks to be a real small flat shim.

Transfer case u joint angle is down 5.3* and the rearend angle is also down but 1.1-1.3 *.

Am I correct in thinking that a 6* shim is needed to point the rear up to oppose the 5.3* down angle of the transfer case? To be within a degree.

I didn’t check angle before as I planned on flipping shims. But since there weren’t ones to flip I couldn’t even do that.

Has anyone else had this strange shim setup from factory? Also just seems excessive in the shim angle needed.

tuckin22 · June 29, 2020

Well. I did some more calculating. Think it’s going to be around 4°.

Read that the leaf spring bolts need to be replaced as they are torque to yield. Anyone know if that is the same for the leaf pack bolt as well as the torque specs? Also if there is a part number for it?

Found part numbers for the u bolts and nuts.
15872657
11549170

Car Dude · July 17, 2020

On 6/28/2020 at 8:28 PM, tuckin22 said:

Well. I did some more calculating. Think it’s going to be around 4°.

Read that the leaf spring bolts need to be replaced as they are torque to yield. Anyone know if that is the same for the leaf pack bolt as well as the torque specs? Also if there is a part number for it?

Found part numbers for the u bolts and nuts.
15872657
11549170

I don't think anyone that did the shim flip put new u bolts or leaf pack bolts on. Not saying that technically you should but I really can't see it being a issue. The factory shim on most trucks were a 2° shim so when its spun the other direction it would be a 4° difference. So if you don't have a shim to start with a 4° should work.

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