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.

Description: 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. T he 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.

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

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:

• These do fit trucks with 56" rear leafs. The brackets are the same, and will mount directly in place of your existing shackle hangers.
   

• 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 popular 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 startsto feel "loose" under hard cornering with body roll.  We've chosen the 4" lift height as the limit for these reasons.
   

• 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.

• 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.

• 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.
   

• Looking to install longer rear springs on your truck? 56" GM springs and the '88-up 64" GM springs are becoming more popular to swap in due to the increased flexability and ride quality. You can use our Shackle Flip for the shackle hanger by putting the brackets on the "wrong" side of the truck to move the mounting point back and/or re-drill the frame to bolt the brackets on wherever you need them. Also check out our longer HD rear shackles for use with longer springs.
   

• 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.
   

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