Shackle Flip™ Kit for '67-up GM Trucks

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.  Check the notes below for details on the Ultimate Adventure K10 rear suspension using our 2.5" shackle flip kit.

Shackle Flip KitDescription: 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.

 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 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".  We now have available a kit to lift your '73-'87 truck or 73-91 K5/Sub 2 1/2".

Please note:  Blazers,Suburbans and some 1-ton trucks had straight front axles through the 1991 model year. They will use the same kit as a '73-'87 of the same duty level.

**We don't recommend using our 4" shackle flip with our 6" Super Shackles, see explanation on that below**

Shackle Flip Instructions

For online installation reviews check out these links:
Shackle flip install by ColoradoK5.com
Shackle flip install by Off-Road.com


Part No.


Amount of Lift Provided by Installing Brackets Finish Price



'73 to '87 K10 & K20
'73 to '91 K5/Suburban

4" Bare Steel $189/pair

  Buy Now


'73 to '87 K10 & K20
'73 to '91 K5/Suburban

2-1/2" Bare Steel $189/pair

   Buy Now


'73-87 GM 1-ton 4" lift

*This kit is for K30 1 tons only, not for a 1/2 or 3/4 ton truck with a 1 ton axle*

4" Bare Steel $189/pair

Buy Now


'73-'87 GM 1-ton 2 1/2" lift

*This kit is for K30 1 tons only, not for a 1/2 or 3/4 ton truck with a 1 ton axle*

2-1/2" Bare Steel $189/pair

Buy Now


‘67-’72 GM 4" lift only

4" Bare Steel $167/pair

Buy Now


‘88-'98 GM 1500, 2500 and 3500 Pickups 4" lift only  (*fits Tahoe and '92-99 2500 Suburban with drilling required)

4" Bare Steel $167/pair

Buy Now


  '92-99 1500 Suburban only, 4" lift

4" Bare Steel $189/pair Buy Now


2000-2007 2500HD and 3500 series GM 4" lift only

4" Bare Steel $195/pair

Buy Now


  '99-06 1500 and 2500 Pickups 4" lift only

4" Bare Steel $189/pair Buy Now

Some other parts you may want to consider with the shackle flip kit are:
New U-bolts
HD Rear Super Shackles
Greasable rear bushing kits

Tech Notes: Shackel Flip Kit Installed

  • For the 73-87 trucks, if you have 8" rear springs you need to use our 2.5" shackle flip and 6" long shackles.  This still gives the same 4" lift height and the extra shackle length will keep the shackles from flipping forward or back when the deeper arch spring extends under load.

  • These DO fit 73-87 (91) trucks with 56" rear leafs. The brackets are the same, and will mount directly in place of your existing shackle hangers.

  • Installing a shackle flip will move your axle forward.  With a stock spring, it's not much, about 1/4" and most people don't notice.  If you're using the shackle flip in conjunction with a lifted rear spring or block, that effect is amplified.  With 8" rear springs and a shackle flip, the axle can move forward more like an inch, so you may want to account for that by re-drilling your spring perches or adding a set of our zero rate add-a-leaves to move the axle back.

  • 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.

  • 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.

  • ***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.

  • Load carrying ability is also a common question.  Basically, if you keep the factory overloads, you won’t have any trouble.  We've designed the shackle angle to retain as much load carrying ability as possible with a lifted 4wd.  The brackets are much stronger than stock and the compression shackle doesn't compromise towing ability, many late model Dodge trucks are setup that way from the factory.

  • 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.

  • 76-91 1-ton trucks require a different flip kit than k5's, k10's and k20's. The kit is the same price, we just need to know it's for a 1-ton when you order it. The difference is that the spring center spacing on the 1-ton axle is only 40 1/2", and on the rest of the trucks, it's 42 1/2". The brackets are a different shape to reflect that.

  • Petersen's Ultimate Adventure K10 used our 2.5" shackle flip with a custom 5" shackle (since we weren't in production on our 6" HD shackles yet) and a '88-98 1/2T truck spring. The front spring hanger was moved forward about 6" and the shackle flip was moved back about 5" to accomodate the extra 12" in length over the original springs. This created a simple, durable and flexible suspension that worked great on the varied terrain of the UA05.

Choose the category you would like more information on.

Doubler™ Dual Transfer Case
Swaybar Correction/Disconnect™ Kit
Shackle Flip™ Kit for ‘67-up GM trucks
Bolt-In Steering Box Brace Kit
1" Body Lift Kit
Competition Style Motor Mounts
Heavy Duty Front Shackles
Chrome Moly Front Axle Shafts
Drivetrain Upgrades
Blazer Soft Tops

Greasable Rear Suspension Bushings
Swaybar Bushing Kits
Body Mounts
Transfer case mounts
Front Upper Shackle Bushing Kit
Spring Bushings
Competition Style Bumpstops
Bushing Assemblies
Tuff Country Suspension