Samurai to YJ Spring Conversion



YJ Springs Up Front

6" Shackles

After breaking one of my front spring I decided to go ahead and convert my front end over to YJ springs.  Here's a before and after shot, the main goal of the conversion was to get better approach angles and more droop.   After mulling it over it looked like the only way to accomplish this without modifying the springs was to go shackle reverse, by extending the frame forward and changing the rear mount I would be able to fit the 46" long YJ spring (stock is 37").  For reference, the bumper is mounted in the exact same position in both shots.

I based my setup off of a how-to email posted on the Pirates of the Rubicon BBS.  Since I didn't want to inboard my springs (like the how-to did) I had to make a few changes.  First I cut off the front spring mount.

Next, using a piece of 2 x 4 x 3/16 steel tubing I extended the frame 4".  I welded a piece of 2 x 2 x 3/16 angle to the side of the frame extension to make a mounting surface for the new spring mount.  The spring mount was made from some 3.5 x 3.5 box steel tubing.  Lastly I cut steel plate and welded it to the bottom of the old frame and new frame extension and to the angle iron, this was to provide extra bracing.

Here's the completed drivers side.  You'll need to put  a notch in the plate for the steering box plate.

One thing you'll need if you do this is a longer drive shaft.  Asian Auto Parts sells the "Sumo" drive shaft, it has 11" of spline, larger u-joints, a smaller diameter shaft on the t-case side for cross member clearance and the mounting flanges have been scooped out to provide the max u-joint clearance.  You can also see my shackle experiment, basically I made a shackle that mounts to the stock location.  I had hoped to help offset the big pinion angle change by keeping the shackle short, and mounted as close to the original location as possible.  More on this later.

The shocks (9012's) just clear the bump stop tower on droop.  Remember with a shackle reversal the axle is going to move diagonally forward on droop and diagonally back on compression.  I notched the corner of the bump stop for safety and also notched the corner of the spring plate.  Speaking of which, the spring plates are from an XJ (I think).  I picked them up at Trailwerks here in town.  They fit the small side of the axle perfect, had to slot the holes for the wide side.

I used a set of 4 leaf packs to start with, hooked everything up and lowered the Zuk onto it's tires.  The shackle immediately collapsed to the frame.  Hmmm, too short.  I decided to go into work on Saturday and figure out what I needed to do to fix the shackle situation, it would be much easier since we have a band saw, mill and welders in the air conditioned shop.

Here's a good shot that shows the amount of spline in the drive shaft.  We had the front end supported by jack stands and the springs were hanging down with no shackle in back. 

Remember the shackle that collapsed? After doing a couple of experiments I made another one about 1/2" longer than the first.  This one put the spring in tension but if you cycled the suspension it slowly collapsed to within an inch of the frame.  On my friend Ken's suggestion we made an adjustable shackle out of one of the short shackles.  As you can see in the second picture we were just 5/8 of an inch off from the length we wanted. 

One thing I tried to avoid by using the short shackle was tipping the pinion down.  Here's what it looked like with the final shackle.  Unfortunately the pinion is tipped down so my caster was way off, it steered like a road grader.  If you attempt this conversion, plan on cutting your front perches and rotating the pinion, also move the axle forward at least an inch more than what I did.  The distance you need to maintain from the rear shackle mount and spring eye is 6", so if you want a shorter shackle you can cut and move the rear spring mount back and adjust the shackle length accordingly.

We were ready for some quick testing.  We were able to lift the front tire 35" with the forklift before the rear tire started to lift.  The tires were inflated to 20psi.  Notice the clearance between the body and front tire.  This static test showed everything to be ok.

Shock clearance is really tight, it was a good thing I cut the corner off the spring plates.  I may move the lower mount outward later.  The second picture shows the YJ spring inverted and twisting.

When I got home I discovered the front bumper still fit.  I could get one bolt in the original lower mounting hole on each side.  I then drilled a new hole into the frame extension so now the bumper doubles as a brace.

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