Drop Shackles

CamGTP · August 1, 2020

Yup, that's how I do it on the ground. Pretty straight forward doing it that way, impact gun makes it a breeze.

hotrodz37 · August 1, 2020

Yup, that's how I do it on the ground. Pretty straight forward doing it that way, impact gun makes it a breeze.

Perfect, appreciate the quick reply!

Any of you guys measure angles before and after? My truck is actually completely stock but they just arbitrarily put a shim in there from the factory which is causing some driveline rumbling on decel. I checked all of the angles today and turns out the shim actually throws the rear working angle out of wack.

These are the numbers I’m working with:

Trans - 5.45* down

Shaft - 5.2* down

Rear end - 1.56* down

So technically speaking mine should be close to spec without the shim completely, or with it spun. Probably easier to just spin it than having to take the centering pin out of the pack completely.

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Zach-91 · August 1, 2020

2 hours ago, hotrodz37 said:

Do you guys have any tips for spinning the shim, or any advice on the best way to do it?

From the looks of it you have to jack up the truck, put jack stands on the frame rails, jack up the rear end, unbolt the u-bolts, let the diff come down on the jack a little to separate from the leaf pack, loosen the centering pin and spin the shim and put it back together?

Am I missing anything or am I making this too complicated?

Thanks in advance for any help!

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Use c clamps to hold the leaf pack together. I also had to use some ratchet straps to pull the axle to get the center pins back in their locating holes. Chock the front wheels and set the ebrake to try and minimize how much things shift around.

hotrodz37 · August 8, 2020

Has anyone spun the shims on a Denali?

I got mine apart this morning, did the pass side and then got to the driver side and there’s this fun bracket for the magnaride. Pretty much makes it impossible to spin the shim without pulling the centering pin out.

I might try and tackle it again tomorrow but dropping the axel low enough below the leaf pack to pull the centering bolt out makes me a little nervous to say the least.

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Ggarcia6493 · August 9, 2020

I just installed the Rough country rear drop shackles on my 2020 Sierra AT4.
I usually do this because i am 6’ 1” and when sitting on the seat with my infant behind me, i had the seat reclined all up on the car seat. So, when leveled, the seating position is more relaxed and upright in my opinion.

I figured i would show it since it was really hard deciding if i should do it since i couldn't find any AT4 with it done. I have it set to the 1.5 hole.

The shackle kit from Rough Country comes with a 1” and 1.5” hole.
I have had it like this for 3 months now and i still dont have any vibration coming from the rear.
I haven't measured it but it looks alot better. The rear sits like 1/2 to 3/4 higher than the front. Which is nice.
The very top is before the kit was installed, the bottom 2 are after the install.

dirtfan21 · March 16, 2021

I just installed RC 1.5” drop shackles on my 2020 RST double cab (4x4) over the weekend, no factory shims on the truck. Those of you that have the “slight” vibration around 30 mph, what are we talking with slight? I feel like a may feel something, but I’m also overly OCD and might be conjuring up a phantom vibration because I’m so worried about it. In other words, the guys that have had vibes, do you really have to pay attention to feel it or is it pretty darn noticeable?

First shackles I’ve ever installed, I usually level the front so I’m new to the “dropped” setup.

Grumpy Bear · March 16, 2021

The rear sits so high so that when carrying a full payload it is near level. That is about 3.5". Driveline angles should not need adjustment with up to a 4" drop. So, I'm at a loss as to the source of this vibration everyone believes is coming from a 2" drop. Well within the 'normal' load height and drive line angles. My K2 is lowered the full four without a pinion angle adjustment and smooth as silk. Can the T1 be that fussy and if so how does it handle a payload stock? I'm scratching my head on this one.

dirtfan21 · March 16, 2021

13 hours ago, Grumpy Bear said:

The rear sits so high so that when carrying a full payload it is near level. That is about 3.5". Driveline angles should not need adjustment with up to a 4" drop. So, I'm at a loss as to the source of this vibration everyone believes is coming from a 2" drop. Well within the 'normal' load height and drive line angles. My K2 is lowered the full four without a pinion angle adjustment and smooth as silk. Can the T1 be that fussy and if so how does it handle a payload stock? I'm scratching my head on this one.

How did you achieve your 4" drop? If you did a flip kit or shackles with hangers then it wouldn't have changed the pinion angle like only shackles do. By installing shackles only, it rotates the leaf springs and differential backwards to drop the 1.5"-2", therefore changing the pinion angle. I found a photo on another site that explains the situation well, see below. I'm still really curious how others feel the "slight" vibration around 30 mph and how severe it is. I'm getting ready to take the truck on a 500 mile round trip this weekend and I'll pull the shackles if I'm actually vibrating, it's just so faint I'm not sure if I really am or not. I don't want to wipe out u-joints on the trip. I ordered several degrees of shims from Belltech yesterday, but they won't be here in time.

Edited March 16, 2021 by dirtfan21

Grumpy Bear · March 16, 2021

3 hours ago, dirtfan21 said:

How did you achieve your 4" drop? If you did a flip kit or shackles with hangers then it wouldn't have changed the pinion angle like only shackles do. By installing shackles only, it rotates the leaf springs and differential backwards to drop the 1.5"-2", therefore changing the pinion angle. I found a photo on another site that explains the situation well, see below. I'm still really curious how others feel the "slight" vibration around 30 mph and how severe it is. I'm getting ready to take the truck on a 500 mile round trip this weekend and I'll pull the shackles if I'm actually vibrating, it's just so faint I'm not sure if I really am or not. I don't want to wipe out u-joints on the trip. I ordered several degrees of shims from Belltech yesterday, but they won't be here in time.

I removed the 1.25" spacer and had Deaver make me a set of 11-1/2 leaf springs with 15% less load that were arched to sit 2.75" lower under the existing back half weight while utilizing Sulastic insulative hangers. This still changes the relative heights of both pinion and transmission tail shaft yokes and their angle of address to each other. I summit that dropping 2,000 pounds in the box will have the same effect on pinion angle the shackle method does without that load.

Yes it does but still well within the optimal range.

dirtfan21 · March 17, 2021

Drove the truck again last night. No vibration on hard acceleration from a stop or while rolling. No vibration at constant highway speeds, 60-80 mph. Only slight vibration, and I mean slight, is at 25-30 mph and it doesn't matter if I'm decelerating or holding constant speed. I have a couple sets of Belltech shims on order and will install when received, problem is they won't be here in time before my 500 mile trip this weekend. I would highly doubt I'll wipe out u-joints or cause damage within 500 miles. Any input would be appreciated.

Dylan199 · August 13, 2021

For those of you that have a 2020 Denali (without factory shim), how are you getting the drivers side leaf spring bolt to line up with the hole in the axle? I just put in shims and because of the adaptive ride plate and shims, the bolt that is suppose to line up the leafs and axle is too short. This worries me because it this can cause the axle to shift while driving. This has also caused my steering wheel to be misaligned.

passat774 · March 3, 2023

For the trucks with no shim, which one do you end up getting 2 degrees? or 4 degrees? I have no shim but a new vibration.

I did not notice the vibration at first, its not super sever just a shutter at 30 mph. It is most noticeable under easy acceleration or deceleration. If you accelerated to 30 mph and stay at the speed you are able to notice it. Or decelerate to 30 and stay at that speed.

Edited March 3, 2023 by passat774

Grumpy Bear · March 3, 2023

1 hour ago, passat774 said:

For the trucks with no shim, which one do you end up getting 2 degrees? or 4 degrees? I have no shim but a new vibration.

I did not notice the vibration at first, its not super sever just a shutter at 30 mph. It is most noticeable under easy acceleration or deceleration. If you accelerated to 30 mph and stay at the speed you are able to notice it. Or decelerate to 30 and stay at that speed.

I dropped mine by removing the riser and a new spring pack from Deaver resulting in about 4" total drop. It required no shim to maintain pinion angle within range. That was like 120K miles ago.

davidr83 · March 3, 2023

19 hours ago, passat774 said:

For the trucks with no shim, which one do you end up getting 2 degrees? or 4 degrees? I have no shim but a new vibration.

I did not notice the vibration at first, its not super sever just a shutter at 30 mph. It is most noticeable under easy acceleration or deceleration. If you accelerated to 30 mph and stay at the speed you are able to notice it. Or decelerate to 30 and stay at that speed.

On the 2020 elevation i had, i used a 2* shim at the initial install and had no vibration at any speed. It was 2WD and the 3.0 Duramax.

I traded it in for a 21 RST 6.2 4WD and used the same beltech shakles on it with no shims and no vibration at any speed.