Another Shackle Reversal

Hello! We have another shackle reversal in progress. :smash:
I have run into a bit of a quandry. Hope someone might offer some ideas.

I am reversing the Shackles on the front of my 67 CJ5. I have an M38A1 that I am using as a guide, as I dont want to effect any lift or drop, but rather making it "stock" as I can make it, as the Jeep already has new 3" lift springs on it.

From the M38A1, I have made locating jigs using the punched holes in the frame and taken a few checking measurements. And I took several measurements on the CJ before the cutting started. So, as of this writing, everything is tacked into place. All dims are checked on the frame and everything seems to be correct. The Jeep sits level, left to right...actually slightly more level than before! And slightly lower in the front.

But...

When I measured from the rear axle tube to the front axle tube, It shows the left side 5/8" forward of the right side! I have been looking the frame over and I dont see anything that would lead me to believe the frame is kinked that bad anywhere. I have rechecked all my dims and Im not seeing the problem. There does seem to be a slight bit more angle back to the left side shackle than the right side. This agrees with what Im seeing when measuring the axles, but not with what my Jigs and my frame measurements show it should be doing!

The springs are the same, both sides, The axles appear to be straight enough to not be 5/8" off. The front axle tube to trans crossmember agrees. And I measured the front axle tube to the front spring eyes of the rear springs and this shows the same 5/8" The measurement of the front spring eyes of the rear springs to the rear frame bushings of the front springs actually shows the right side 3/8" farther forward than the right! (sheesh...thats confusing!) But, a note here, the M38A1 shows that same 3/8" stagger within 1/8"!

Could these holes not be accurate "tooling holes"? (see pic). Could they be different from side to side?
Should I just move the left side forward, and the right side rearward until it is square to the rear axle, making sure the shackles have the same angle.
Can anybody tell me the correct, stock, unmodified distance from the front of the rear axle tube (Dana 44) to the rear of the front axle tube (Dana 25, or 27)?

Thanks for any help ya'all can offer here!

Scott :? :?

 

If possible, measure from the rear main spring mount to the front main spring mount to see if they measure out. Having the shackle mount off a little shouldn't really have anything to do with the axles not being parallel. Mostly that will affect height (slightly) and the shackle angles will not be the same. Also, if you measure in a straight line from eye to eye on the springs and then measure the springs along the curve from eye to eye you'll get a longer measurement along the spring. Your shackle length is somewhat determined by the difference in measurement. ie: If your spring measures 30" eye to eye and it measures 36" along the arc, it is possible for that spring to grow almost 6" under compression. If you setup that spring with the shackle vertical your shackle would need to be 6" long to accomodate the growth of the spring. Your front main mount looks too short to maintain proper kingpin castor. That's why most conversion kits have taller main eye mounts, which is why most shackle rev. give you about 1 1/2" of lift. If you are using a M38 frame for reference you'll notice the the bushing for the shackle is mounted up in the frame. It doesn't use a shackle bracket mounted to the bottom of the frame. That's why a M38 from main eye mount is shorter than most after market kits. Also, the longer your shackles the more your pinion drops toward the ground. The longer the front main eye mounts are the more the pinion points up away from the ground. You need to maintain about 5 deg negative castor on a D27 to have it steer like it's supposed to.

 

Thanks for the reply. Decided the problem is that the front of this frame is pretty bent up and has been rewelded at some time. Possibly shortened!

So I just squared it to the rear, and checked all the points to the rear points. Only had to move one side 1/8" back and the other side 3/8" forward. Shackles hang good, Put my extended shackles on it (4 5/16" CTC). All sits level and looks correct, so I burnt it in! Drives fine, but, I will need to put my caster shims in and get the Driveshaft built and its done!

Pics forthcoming

Scott

 

Sounds like you got it wired.

 

Thought I would shoot some pics here. This set up doesnt offer any lift at all. Actually, with the arched 3" lift springs, it was near 1" down in the front with the stock shackles. So the 2" longer shackle brought it up to level (BTW...they are 4 3/4" ctc, not 4 5/16").

Was wondering why the short shackles worked on the military Jeep. My guess is the stock M38A1 springs are near flat, so they really dont grow any significant length in compression?

Scott :driving: