I really didn't want to send the money for some new or custom springs, so I began looking into various pivoting or double shackles.  At the time, no one made any such shackles for the Land Cruisers.  Then I heard about a company called Swamp Frog Industries (SFI) that had just released their line of HyperShackles for the Land Cruiser, Jeep CJ/Wrangler, and Samurai.

So I contacted SFI and inquired about thier HyperShackles.  They told me that the HyperShaclkes were avaliable in lengths from 4.25" to 6.5" from shackle pin-to-pin at rest and extended lengths from 9" to 11" depending on specific applications.

The designers of the HyperShackles wanted to build their shackles to be bulletproof and superior in strength of all other pivoting shackles on the market.  In doing so, they used 1/2" thick steel plate for the shackles and a piece of schedule 40 pipe for the pivot point.  They also decided to use some 5/8" shackle bolts for the FJ40 applications.  They could not go much bigger than the 5/8" bolts since the OD of the shackle bushings are only 1" on most FJ40 applications.
 

Installation:

The installation of a pair of shackles can be a quick and painless procedure or it can be a total nightmare if the shackle pins have bonded with the bushings.  Fortunately for me, I had just removed my stock shackles a few months back so I did not have to fight the frozen bushings this time.  I was able to install the HyperShackles in just under 30 minutes.

To get ready for this project, I locked the hubs, shifted into 4 wheel drive, parked the Cruiser in the driveway, and blocked the front wheels.  I raised the rear of the Cruiser and slid some jack stands under the frame for added safety.  I used my Hi-Lift to raise the rear of the Cruiser just enough to 'unload' the springs and make it easier to remove the shackles.  Then I unbolted both shackles and remved them.  That was so much easier than the last time.
 

The shackles that I just removed were some home-brew shackles that I had made after I bent the stock shackles beyond repair.  Like most aftermarket shackles, I used 9/16" SAE bolts for the pins because I could not find any 15mm bolts (stock size) locally.  This required me to switch the shackle and spring bushings to some aftermarket ones that had an ID of 9/16".
 

Since the HyperShackles use 5/8" shackle bolts and my current shackles used 9/16" shackle bolts, I had to use different shackle bushings that had an ID of 5/8".  In the pictures you can see the 9/16" bushings in red, and 5/8" bushings in orange.  I was lucky to have a full set of 5/8" shackle bushings lying around since the HyperShackles do not come with bushings.
 

I ran into some problems that I did not forsee when it came time to install the HyperShackles on my FJ40.  I was using some 2 1/2" Rancho leaf springs and the spring bushings are 1 3/8" OD and 9/16" ID.  I quickly ran inside and searched for some alternate bushings that had the correct 1 3/8" OD and 5/8" ID to work with my new HyperShackles, but I did not find any.  I decided to see if I could drill out the Rancho poly bushing to 5/8" by using a 5/8" wood drill bit.  I was worried that the poly bushings would tear, but with the wood bit, it was more like reaming out the hole.  This would not have been an issue if I had stock springs since many of the Land Cruiser vendors sell stock spring bushings with a 5/8" ID.
 

As I installed the HyperShackles on my Cruiser, I coated the shackle bolts with some grease to help keep the busings lubricated.  When I installed the lock nuts on the shackle bolts, I made sure they were only snug against the shackle.  You do not want to over tighten the nuts or you could bend the ends of the shackles inward.  I have seen this on lots of the braced or 'H' style aftermarket shackles.
 

Impressions:

"Wow, these things are beefy" was the first thing out of my mouth when I opened the box.  These 1/2" thick shackles weigh about 15 pounds each.  The craftsmanship seemed to be high quality as all the corners and edges seemed laser cut and the motion of the shackles werre very smooth. 

As soon as I was done installing the HyperShackles, I used a my Hi-Lift to raise the rear of my Cruiser to see how much more potential suspension travel is possible.  You can see the difference between the before (far left) and after (near left) pictures.  I think I might need a longer Hi-Lift.
 

As the suspension cycles, you can see the HyperShackles begin to open and allow the axle to droop more than a conventional shackle.  In the pictures below, the shackle extends from 4.25" at rest to 11" at full droop.  Because of the increased droop, I had to move my lower shock mount from the u-bolt plate to the back of the spring perch.
 

I thought that the shackles were a little noisy on the road and on the trail due to the fact that they hit the frame as the suspension cycles.  In the above pictures you can see that see that the shackle is sitting against the frame in the left picture and it is away from the frame in the other pictures.  This noise can be reduced by adding some kind of bushing between the frame and the shackle. 

The shackle hitting the frame like this is an integral part of the anti-inversion feature of the HyperShackles.  The last time I was on the Rubicon, I had inverted my shackles twice.  When a shackle gets inverted, the spring is forced against the frame and there is a great possibility that your spring will bend or break if it is not corrected right away.

With my Cruiser now equiped with HyperShackles, I noticed that I could go further along some of my favorite trails without having to use my air locker.  There was no doubt that the added droop provided by the shackles gave me the necessary traction to keep moving.  The limiting factor in my suspension setup was the fact that the Rancho springs were a little too stiff to allow the full potential of what the HyperShackles could deliver.  I think with softer springs (stock springs) I would have seen even more droop.

Here you can see the HyperShackles have a built in gap of 1/4" between the bushings and the shackle.  This is designed to allow the shackle and spring to twist somewhat since the shackle itself will not.  I did not notice any adverse effects due to this gap, but it might cause the bushings to wear out faster than normal by putting more pressure on the shoulders of bushings.
 

One thing that has me worried about pivoting type shackles is when backing down really steep hills, there is a potential for them to open up a little on the rear spings.  I have not seen this first hand yet, but I will keep an eye on it and see what happens.  I have had these shackles on for 6 months now and I have punished them numerous times on the Rubicon, through Gold Lake, and all over Hollister Hills, and I have not had any problems with them.  Overall, I am very satisfied with the quality of these shackles and they performed like I had hoped.