Mighty Mo and Friends

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Shackle Reversal on a CJ2A


Design considerations:

Without going too deep into vehicle suspension design, to maintain the caster, the spring eyes of a spring need to be the same distance from the ground as they were originally. The Willys service manual says the vertical distance between the front spring mounts is 4 5/32". I measured the distance the shackles raised the front vehicle and found this was 2 7/16". Now I know the front of the spring needs to be 1 23/32" higher than the rear when I am done.

I wanted to include a 2 1/2" suspension lift in this project. Therefore to keep the vehicle level, I needed to keep the lift provided by the shackle reversal to zero. This was accomplished by borrowing the concept from M38A1 and early CJ5. They both had the shackles at the rear of the spring. Oddly the upper mounting point for the shackle is through the frame.

I really wanted a 3"+ lift so I decided to use longer than stock shackles to gain the extra the springs would not provide. Stock shackles were 2 5/8" center to center. I knew I would need to shim the spring hanger from the frame and wanted to use square tubing for the strength. Therefore this dimension needed to be a standard size. The shackle length would be the variable. Longer than 2 5/8' but not so long as to be weak.

Mighty Mo had a radical front 'lift'. This would be eliminated with this project.

5" block and 1 1/2" longer shackle

3" block at rear of spring

Also the original springs were from a CJ5 and were not the right length. I wanted to install the CJ2A lift kit. This meant nothing up front would assist in positioning the front spring hanger. Position of the front hanger, both horizontal distance from the rear shackle mount and vertical distance from the frame would need to be determined. Below is the CAD drawing showing the original, as Willys designed it, and with the suspension lift.

To begin with I drew the original as close to stock as possible. The dimensions I could not get from my Jeeps or manuals I had, were provided by the good folks at Willys Tech. These people are a wealth of information. Then I modified the drawing to reflect the changes I wanted. I had to keep the spring eyes same distance from the ground to maintain the design caster. It turned out that a 4" block added between the frame and the rear spring hanger when accompanied by a 4 1/4" long shackle would keep the caster right and provide about 1 1/2" additional lift, over that provided by the springs, at the front bumper for almost 4" lift up front. The 4 1/4" longer shackles were used on the rear and they added about 1" additional lift there for a total in the rear of just over 3 1/2" lift.

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Copyright Richard N. Meagley Sr.
Last revised: May 25, 2007.