Shackles

Rear leaf spring shackles are commonly used to “Level” trucks. For those of you who just can’t stand the “stink bug” look of factory stances, the lowering shackle is for you! Typical drop is two inches and fairly simple to install. You simply remove the factory shackle and replace it with a longer drop shackle. Be sure to use the one designed for your particular truck!

The leaf spring shackle is located on the rear of the leaf spring and is the only part of the rear suspension that is designed to move. When you hit bumps and dips, which cause the rear end to move up and down the leaf spring actually gets longer and shorter relative to the frame. It is the shackle that pivots forward and back with the leaf spring while being firmly attached to the frame. A good tip when installing shackles is to lubricate the bushings and bolts and be careful to not over tighten. It is possible to tighten so much that the shackle will not pivot, which can cause the truck to ride horribly, and affect ride height. Of course you the pivot bolt needs to be tight and you should use the factory locknut, just don’t set your pneumatic wrench to kill and run it down until it stops!

EYE HANGERS

Correctly referred to as spring eye hangers, this is the bracket that Secures the front of the leaf spring to the frame. There is no movement here, this is a fixed mount. There is a little movement in the leaf spring bushings as the shackle pivots back and forth so it is still a good idea to apply a little lubricant to the leaf spring bushings and not use a vulcan death grip when tightening. The typical drop is two inches but some applications have multiple settings so you may adjust the amount of drop to better suit your needs. This part is rarely used by itself to lower, primarily because of the labor to install, but is teamed up with shackles to complete “Hanger & Shackle” kits, which are very popular for mild drops. The range of drop for this type of kit is three to five inches depending on the application.

FLIP KITS

The first thing to get off the table regarding “flip kits” is nothing is actually flipped! Simply put a flip kit moves the axle from beneath the leaf spring to on top of the leaf spring. The devil is in the details here and how its done is very important. When you place your axle on top of the leaf springs there are two very important things to consider. No. 1 you must move the rear axle back towards the rear of the truck, away from the transmission, around ¾ of an inch. This is done because your drive shaft actually becomes longer when you “flip” your axle. Say what! Gets longer, how? You’ll notice the splined slip joint in the front of your drive shaft. It’s there to allow the drive shaft to move towards and away from the transmission as the suspension cycles up and down. If you were to support your truck by placing jack stands under the frame (both sides) in the rear. Then, with a floor jack supporting the rear end, remove the lower shock bolts and let the rear end down with the floor jack and look at the splined slip joint, you will see a fully extended slip joint. Now slowly jack the rear end up with the floor jack and watch the slip joint contract. If you could jack the rear end up to the point where it was level with the transmission the splines might completely disappear and the drive shaft would be forced into the transmission. This is not a good thing and why you need to move the axle back away from the transmission when you install a “flip kit”. The axle locator brackets accomplish this, generally a “U” shaped piece that sets on the leaf spring, over the center bolt. There is a hole in the factory axle locator which is centered, and you will see that the hole in the axle locator from the flip kit is offset. That is how the flip kit moves the axle back away from the transmission. It is very important to make sure you install the axle locator bracket correctly with the offset hole over the leaf spring center bolt spacing the axle to the rear. Now the second consideration when installing a “flip kit” is pinion angle. The typical drop you can expect from a flip kit is in the 5” to 8” range, depending on the thickness of your leafspring pack. And while the rear of a pick up truck is designed to operate in a wide range of ride heights (empty to overloaded) it is still necessary to establish an optimal static pinion angle. Axle locating brackets in most flip kits have a built in angle, by having unequal length legs in the “U”. This works pretty good most of the time, but not all trucks are created equal and often you need to adjust the pinion to get rid of a pesky vibration. You can buy pinion “shim kits” that come in 2, 4, and 6 degree packages that need to be installed between your axle locator bracket and the leaf spring. Better that that, DJM makes their flip kits with adjustable axle locator brackets. You have the ability to rotate your axle to the proper angle and then lock it in place. This is the best way to deal with pinion angle. Oh one more thing about vibrations, if you have a two piece drive shaft and your having very low speed vibrations it is almost always caused by the carrier bearing. The bear where the short front drive shaft and the longer back drive shaft connect. Typically raising this “carrier bearing” up towards the bottom of the bed between ½” to 1” will ride you of this inconvenience. There are kits available for this condition also. Wow sounds like I should just use a lowered leaf spring and forget all this worry. If it were that simple everyone would do it! You have to consider the exact same things with lowered leafs as you do with flip kits (or hangers and shackles). You lose travel and effect the pinion angle. Lowered leaf springs do not have a great reputation when it comes to ride and you don’t have the same load carrying capacity as with factory leafs. It seems the best choice for lowering leaf spring applications is still flip kits. Do I have to cut my frame? Only if you have lost enough travel to make your ride harsh. Usually a six inch drop of any kind causes you to need to “notch” the frame to gain travel. You actually cut relief (notch) in the frame directly above the axle and install a frame support bracket. The frame support is a big steel reinforcing plate that bolts to the frame more than making up for any loss of strength that may have resulted from the “notch”. These are typically 3/8” thick plates bolted in with at least 8 - ½” hardened bolts washers and locking nuts. Resist the temptation to weld these plates in. Your frame is probably tempered which means you can weaken it by applying heat. It’s a little more work to drill the holes but a lot safer. Here’s a really good tip – ALWAYS “FLIP YOUR AXLE BEFORE INSTALLING YOUR FRAME SUPPORT”. Remember the axle gets moved towards the rear when flipped, besides you can more accurately locate the “notch” if your axle is in place. Well you have moved your axle from below the leaf to on top, and notched and reinforced the frame what else is left to do? Some, but not all “flip kits” have “shock extenders” which of course do not really extend shocks. What they do, do is reposition the lower mount so they become more vertical. Shocks just are not very effective if they are laid over nearly horizontal, some kits only require one shock to be “extended”. Having done that its time to test drive. Another good tip is to check the tightness of all bolts (including the axle U-bolts) after you have put a hundred so miles on your lowered truck.

LOWERING BLOCKS

Commonly known as “Universal Lowering Blocks”, these babies will fit any truck with 2 ½” wide leaf springs. Of course, in order for them to work your leaf spring must already be on top of the axle. They are placed between your axle and the leaf spring and it lowers your truck by spacing your axle up towards the bottom of your truck. Aluminum blocks originally popular with the mini-truck crowd have been upgraded to all steel blocks to accommodate the big trucks. Basically it is a very good idea to use steel in all applications except mini trucks with 4 cylinder engines.

COIL SPRINGS

Chevy started using coil spring rear ends in 1963 and they came back to be the OEM choice with SUV’s in 2000. Coil springs come in several different heights, from a “leveling spring” (like shackles) to big 5” drops. Depending on the SUV and depending on the drop you will probably need additional parts to keep trailing arms, anti-swaybars, and shock absorbers working optimally and not getting tangled up with each other.

REAR KITS

In most any drop of a coil spring rear end more than 2” you should have a rear kit that will offset the rear trailing arms down away from the frame using brackets. And anti-swaybar endlinks that will move the bar to either port or starboard to allow the bar its full range of motion without contact. It is the biggest mistake in lowering these truck rear ends to not use a rear kit. Your passengers will know right away if the SUV their riding in does not have a rear kit installed.

PINION SHIM KITS

As we discussed in the “flip kit” section having the right static pinion angle is very important. If you don’t have the very cool DJM axle bracket then you will have to depend upon cast aluminum pinion shims. They are available in 2, 4 and 6 degrees and must be placed between the axle bracket and the leaf spring. The best kits offer a bushing to allow for different spring center bolt heads.

 

TRANSMISSION CROSSMEMBERS

In some rare but absolutely necessary cases you must, after lowering your truck, reposition the transmission brace. If you don’t you may find yourself in a very embarrassing situation high centered in the mall parking lot on a “speed bump”.

Questions? ask tutorialdude@calmaxsuspension.com