Shackle Reverse

 

   
 
 

Shackle Reverse

I have been running a leaf spring with a shackle reverse in the front of my rig for quite a while now.  I was after as much front end clearance as possible along with a lot of wheel travel and this setup has delivered.  I still manage to get into spots where no amount of clearance would work as seen in the first picture, no suspension is perfect.  A few advantages to doing a shackle reverse:

  • When climbing, the front wheels walk forward, extending your wheelbase slightly which helps climbing obstacles (see second picture above).

  • When pushing the front tires into a vertical wall, the tire gets forced up and back, again helping you climb.  With a shackle in front, the tire gets pulled down and back due to the front mounted shackle extending.  This behavior bends springs.

  • A small shackle provides a lot of articulation, no need for folding shackles or other goofy gimmicks.

  • On road, the ride is smoother since the forces generated by bumps is soaked up towards the rear mounted shackle instead of straight up into the frame.

  • Allows the best approach angles with leaf springs if setup correctly.  If you do hit the leaf springs on an obstacle they can be used as ramps.

Disadvantages:

  • You may experience brake dive, although I suspect this is more a brake proportioning issue.  With my Toyota axle's larger brakes I haven't experienced this.

  • A long travel front driveshaft is required up front to handle the front axle travel. Keep in mind the pinion angle may need to be adjusted, make sure and check for u-joint bind at full droop.

  • For hardcore four wheeling, a military wrap shackle is highly recommended to keep the spring from being bent when the front axle walks forward.  Again, shorter shocks can be used to limit forward travel.

  • The front axle needs to be moved forward to gain more clearance on the inner fender well when the wheel is stuffed.  Bump stops will also take care of this problem.

Back when I had sheet metal I clearanced the front edge of the wheel well to gain tire clearance when the tire is stuffed.

I purchased the front long travel driveshaft from Asian Auto Parts of Az.  Gloeco is the actual mfg.  They (Gloeco) also offer the shaft with a solid shaft on the splined end if you ask for it.

 

I am using custom leaf packs to locate the front axle.  They started life as a rear, 5 leaf YJ spring pack  (purchased from JC Whitney #07ZX2051U) but I had a local spring shop remove the top two leafs and replace them with a pair that had a military wrap.  This gives the main leaf a lot more support and solved the problem of bending a main leaf from time to time.  I also had the spring shop upgrade the center pin from 5/16 dia to 3/8 dia.

These pictures were all taken after I re-tubed my front axle so I am using slightly larger u-bolts than before.  The u-bolts shown are from the rear of an F250.  You'll also not we turned the pinion up when we cut and turned the knuckles.  I went a little too far and should have only turned them about 10 degrees.  The extra angle hasn't hurt anything and the front driveshaft no longer vibrates at speed when the hubs are locked in. If you do cut and turn the knuckles or want to rotate the housing, you want to aim for 1-5 degrees of positive caster angle.  This can be measured by placing an angle finder on the top of the steering knuckle (with the steering arm removed), you want 1-5 degrees shown on the angle finder with the front of the knuckle higher than the rear.  

If you just rotate the housing and re-do the spring perches you will have a hard time getting a u-bolt on the passenger side next to the differential housing.  To solve this problem, I made two small blocks, tapped them for 1/2-13 threads and welded them to the housing.  I am using a u-bolt on the outside and two grade 8 1/2-13 bolts for the inside.

Here's a picture showing the blocks in back of the axle and in front of the axle.  The spring perches I used were some generic ones designed for a 2.5" wide spring (might have been Conferr).  I had to custom grind the passenger side spring perch and the differential housing to get it to sit flat at the angle I turned the housing.

Up front I am running 10" travel Bilstein 5100's.  They are tipped back approximately 12 degrees.  I aimed to have 5" of shaft showing at rest.  I could run longer shocks but I wanted the shocks to limit down travel to keep the axle from walking too far forward.

For the rear spring hanger base I used a piece of 2 x 1 x .18 wall rectangular steel tubing.  Next, I cut two notches for the DOM tubing I used as the bushing holders. I installed two bushing tubes to allow for some adjustment.  You would think all YJ spring packs are equal but from what I have seen they vary enough to throw the shackle angle off when replacing spring packs.  

Both of these pictures show measurements taken from the floor.

This picture is a measurement taken between the center of the rear spring hanger bushing and the front spring bolt.

Lastly a dimension showing how far forward I mounted my front spring hanger in relation to a stock frame reference point and a measurement from the floor.  I have no idea if these measurements will work with a stock steering box but I suspect you would need to move it further forward on the frame rails.