Shackle Flip Kits for '73-91 GM Square Body Trucks
Lift the back of your truck with our shackle flip brackets! Can be used alone or in addition to a lifted spring or block.
As seen in Petersen’s 4WOR, 4X4 Power, Off-Road.com and ColoradoK5.com. Turns the factory rear tension shackle into a compression shackle for 2 1/2 or 4 inches of lift without using blocks. Bolts to factory holes with Grade 8 hardware for a stronger than stock mounting system. We also carry stock length u-bolts for installations replacing lift blocks.
How many of you want to get rid of your rear blocks? Due to popular demand, we’ve developed this kit to eliminate rear blocks. They're also an inexpensive and effective way to lift the back of your truck.
Our brackets bolt to the frame in the factory spring hanger holes and "flip" your factory tension shackle over to a compression shackle. The kits give four inches of lift (we do have 2-1/2" lift versions for some applications) so they allow you to use stock springs for a 4" lift, 2 inch springs for a six inch lift and so on.
Eliminating lift blocks helps reduce axle wrap and using flatter springs gives better ride quality and suspension flexibility. This kit is extremely durable with fully welded, ¼" gusseted brackets and all grade 8 mounting hardware. We even moved the mounting point forward to give you a better shackle angle. That’s why the brackets don’t look "straight".
For online installation reviews check out these links:
Shackle flip install by ck5.com
Shackle flip install by off-road.com
Installation of the shackle flip kit requires removing the rivets from the factory frame brackets by air chisel, grinder, or your favorite other method. At that point, the holes are drilled to clear the bolts and the brackets are bolted on. This will most likely require removing the dropping the gas tank down on Blazers and Subs for access to the bolts. We've had good luck just hinging the tank on it's mounts so we don't have to disconnect the wires and hoses.
Does installing a shackle flip kit moves the axle forward?
Yes, shackle flip kits do move the axle forward by nature simply because they only drop one end of the spring. How much depends on how else the truck is lifted.
If the shackle flip is installed on a stock spring only, it moves the axle forward ~1/4". Many people don't even notice but we do offer axle offset plates to push it back if you'd like.
If the shackle flip is installed in addition to a block or lifted spring, the effect is amplified and the axle will move further forward (the more lift in addition to the shackle flip, the more this happens). We do offer axle offset plates to push it back if you'd like. For example, using our shackles/shackle flip plus 8" rear springs will move the rear axle forward ~1-1/2".
Do shackle flips have an impact on load capacity and towing?
Other than lifting the truck, a shackle flip doesn't impact load capacity or towing ability. It's the same spring and will behave like stock other than that the truck is now lifted. If you have concerns on towing with a compression shackle (i.e. shackle flip), look at any of the newer heavier duty Ram trucks.
Does installing a shackle make the truck ride better and flex more?
No, for the same reason that shackle flips don't hurt load capacity and towing. It's the same spring, we're just using a bracket to drop it down to get the lift.
Notes on installing a shackle flip with 8" rear springs
If you're using our shackle flip along with 8" or taller springs, we highly recommend that you use the 2-1/2" lift version along with our 6" shackles. Without them, you run the risk of the shackle moving "over center" and flipping forward. The longer shackles fix that.
What about pinion angle?
Pinion angle is a common question with this kit. The quick and easy answer is that there is no quick and easy answer. Proper pinion angle depends on drivetrain length, wheelbase, gears, tires, vehicle speed and more. It usually boils down to what works for your truck. In general, the shackle flip sets the pinion angle about right for most 4" to 6" lift Blazers and shortbeds, especially the later models with the aluminum transfer cases. Longbeds and Suburbans will probably (but not always) need to shim the pinion down a few degrees for best driveshaft alignment. If you have questions about how to set up driveshaft angles, visit www.4xshaft.com. That's Tom Wood's Custom Driveshafts website and has a good tech section with info on setting driveshaft angles.
Can I get more than 4" of lift using the shackle flip brackets?
You may wonder why we don't have a Shackle Flip kit for more than 4" of lift. The reason is that to gain more lift, the end of the spring has to drop down twice the desired lift amount. In other words to gain 1 extra inch, we would have to drop the rear of the spring a full 2 inches. This drop at the tail of the spring can become a ground clearance problem and promotes roll-oversteer which is a handling problem in which the rear of the truck starts to feel "loose" under hard cornering with body roll. We've chosen the 4" lift height as the limit for these reasons and this is also why we typically don't use our 4" shackle flip with our 6" Super Shackles.
Does the shackle flip put more leverage against the bushings and make it less stable?
There is no more lateral lateral motion of the vehicle than with the stock tension shackle bushing setup. It may look as if the axle could move side to side easier, but the only thing that puts more leverage on the bushings is the additional ride height, which you also gain with blocks or lift springs.
Can I use the 1 ton shackle flip to avoid moving springs perches when swapping a 1 ton rear axle into my 1/2 ton?
Not really. The 1 ton shackle flip would address the spring pad difference at the back but keep in mind that the hanger at the front is different too. So you'd have to source 1 ton brackets for the front of the spring too and most find it's easier to just move the perches.
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