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Heavy Duty Shackle Installation 2011-2021 GM 2500/3500 HD

Disclaimer: John C Garage cannot be held responsible to injury, death or damage done to you or the vehicle during installation. Following these steps is at your own risk!

Tools required:

  • One floor jack (Rated for 2 ton or more) with 2 jack stands

  • 1/2” impact/long ratchet along with misc size extensions

  • Torque wrench that goes up to 175 ft lb

  • 15/16" socket and wrench

  • 27mm socket or 1-1/16" SAE

  • A ratchet-strap

  • Socket to remove your lug nuts (this may vary depending on truck)

  • Blocks of wood

Step 1: Jack the rear of the truck up until the rear tires just make it off the ground. You will want to jack it up by either the hitch receiver or frame. (if you jack it up by the rear axle, you will have to get it high enough so that when you put the jack stands under the frame, the axle does not sag enough for the tires to touch the ground.) This is where the blocks of wood might come in handy. If you put the jack under the hitch receiver, use a bigger block of wood to fill the gap between hitch and jack.

Step 2: Use two jack stands and put them under the frame of the truck so they are supporting the vehicle up in the air with the two rear tires off the ground and the suspension fully unloaded. Now you can remove both rear wheels from the vehicle.

Step 3: Start on either side of the vehicle you prefer. You will need to support the rear axle so you can unbolt the leaf pack. Place the jack under the rear shock mount of whichever side you start on. Once the jack is under the shock mount, go up with the jack just until it touches the mount. ***Do not go up any further at this point with the jack***​​

Step 4: Using a ½” impact or long ratchet, take the two 27mm nuts off the rear u-bolt ONLY. Once those two nuts are removed, you can pull that u-bolt out completely and set it to the side. **WITHOUT** unbolting the front u-bolt, you should be able to swing the carrier with front u-bolt down and move it forward, resting it on the leaf pack. This will help with the installation of the parts going back on and exactly where they were before being disassembled.

Step 5: Using a 15/16" socket and wrench, remove the two nuts that are used on the hardware that fastens the shackle to the frame and leaf pack. You can leave the bolts themselves in, just remove the nuts. At this point you might be wondering how you are going to remove the upper shackle bolt since the frame is in the way and will not allow the bolt to be pulled out. Do not worry about this just yet! Step 6: Remove the 15/16" bolt at the front of the leaf pack. This will need to be removed completely! Step 7: Remove the bolt that goes into the lower bushing of the shackle, pushing it in towards the spare tire. Once this is removed, the leaf pack is now unfastened from the vehicle completely. You can tilt the whole leaf pack 45 degrees towards the outside of the truck and that is how you will be able to remove the upper shackle bolt! Remove this upper bolt, then the factory shackle can be removed completely from the vehicle. Now with the leaf pack tilted 45 degrees still, you can put the new shackle in and the upper bolt going the same way as it came out! **This is specifically designed by GM and should not be changed! **

Step 8: For 2" shackle installation *ONLY*, at this time you can fold over the pinch weld with a large set of pilers. You can also use a block of wood and hammer to fold it over. Applying a small amount of grease on the lower shackle bushing ends will help it slide into place a bit easier. Tilt the leaf pack back to its normal position while guiding the new shackle into the hanger bracket on the frame. *This is usually a very tight fitment* You can now put that bolt back in for the lower shackle bushing. Both 15/16" nuts can be screwed on hand tight at this point for the shackle hardware. Step 9: Now you will need to install the front portion of the leak pack. By doing this, make sure the alignment pin in the leaf pack is lined up and dropped into the hole on the axle itself. You will need to use the jack that is under the shock mount and jack up until the front leaf pack bushing meets up with bracket mount hole. You might notice at this point; the whole assembly needs to come back to line up the bolt hole. Using a ratchet strap, you can go around the hub of the brake rotor and back to the hitch receiver and pull it back until the bolt hole lines up. Insert the front leaf spring bolt, and there will be a nut on the other side to be used. Make sure the nut is facing with the arm towards the center of the vehicle. The arm or tab on that nut is used to press against the frame to keep it from spinning, so that a wrench or socket is not needed when tightening.

Step 10: With the front u-bolt still intact with the carrier, you can slide that back to its normal position and swing the carrier back under the axle. **At this point, you can look at the paint on the axle or markings to know exactly where the carrier used to be! ** You can drop the rear u-bolt back into place and then screw the 27mm nuts with their washers back on. Make sure all four 27mm nuts are tightened even though you did not loosen the front two. Usually these will need to be tightened a small amount just from being removed and put back on. Torque spec is 175 ft lbs. for these nuts.

Step 11: Next you will repeat process 3-10 on the following side! Step 12: You can now put the rear wheels and tires back on. Once on and fastened to the vehicle with the lug nuts tight, you can return the truck to the ground by removing the jack stands and lowering the vehicle with the jack. With the truck back on the ground, and suspension fully compressed with the weight of the vehicle, you can go through and now tighten all 15/16 bolts and nuts for the shackles and front of the leaf pack. The purpose of this is tighten the suspension in a "neutral position". Torque spec is 60 ft lbs. for the shackles, top and bottom. The front leaf spring fastener can be torqued to 90ft lbs. Completely optional - If you want to adjust your front torsion keys (for a more leveled look) the bolt size is 21mm. To adjust the torsion keys up, I place a jack under the front of the vehicle and jack up until the pressure is off the front suspension however the tires do not need to leave the ground. With jack stands under the front of the truck, you can turn in the torsion bolts. Always tighten them the same amount on each side. Typically, you will need to go in 4-5 full turns to get the front close to level with the rear when the keys are in factory position. Again, this is completely at your discretion and does not need to be done! On my personal truck I leave roughly 1-1.5” difference from the front to rear for towing purposes.

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