Front axle and spring/shock problem - Any ideas?

Hi all, and thanks for any help in advance.

1969 Jeepster, 1-3/4" wide front springs, 6 leafs on front spring packs, 3" long shackles. D27 with stock panhard rod.

Went to measure compressed / extended and sitting height for new front shocks, and here are my numbers:

(measured from stock upper pin mounts to stock spring plate mount (front))
Sitting Height: 17-3/8"
Compressed: 14-3/4"
Extended: 19-1/2"
Total Travel: 4-3/4" (Is this normal???)

I put the jack under the spring plate on driver's side and lifted it until the DS tire *just* came off the ground. Compressed value was only 16". What ??! Only 1-3/8" of up-travel? The axle was still 3" from the bumpstop!

Nothing seemed to be obstructing the travel. So I continued jacking the wheel up until the PASSENGER side tire just lifted off the ground, and remeasured. 14-3/4" compressed.

I then jacked up the frame from the front bumper attachment point, and shock measured 19-1/2" at full extension. Thinking the shocks might be limiting down-travel, I removed them, but max extended length stayed at 19-1/2."

What is going on here? Why is the up and down travel so limited? 4-3/4" seems awful short flex for a Jeep.

I did this exercise from both sides and the measurements were essentially the same (within 1/8"). I removed the blown monromatic J1000 shocks (12" compressed-20" extended) and remeasured, with all same results. The panhard rod to the D27 cycled up and down freely and nothing seemed to be obstructing axle up or down travel. NO SWAY BAR, either.

I am stumped... The only thing that I can think of is the SPRINGS are limiting travel... So my next thought was that the springs are not stock...(of course PO is no help)

A couple of questions:

1) The springs have little black plastic sheaths under each leaf - are they original or new(er) springs?
2) Is the 17-3/8" sitting height (from shock mount to shock mount) normal, or are these "lift" springs?
3) Could it be the 6-leaf HD springs limiting travel? When fully jacked up, with PS wheel off the ground too, the springs still had an arch to them... (is that normal?)
4) Is there anything I can do to increase the flex? remove a leaf?
5) Finally - what shock travel lengths should I go for? 13-1/2" - 20" and call it a day?

This baby Jeepster of mine is giving me fits at every turn... and THANKS for any help here, fellas.

 

You tried this with the shocks removed?

I guess you want the spring to compress fully rather than to lift the other wheel. I would be surprised if this happened. The critical quantity is the rate of the spring, and how it changes as the spring compresses. Ideally the spring will get stiffer as it compresses, so that it slowly transfers the impact load from the wheel to the chassis. If the rate did not change, then the slightest bump would drive the axle all the way to the stop. It is not surprising that the other wheel starts to lift before the spring is fully compressed, when being lifted by a jack.

With the shocks, you will be limited by the distance between the mounts at full compression, ie when the axle stop is fully compressed by the axle. You don't want the shocks to bottom out - instead you want the frame bumpers to stop the axle. The extended length can only be, at most, twice the compressed length. If the shocks extended length limits the downward travel of the spring, that's ok - it's better than the shocks bottoming out.

 

Shocks installed, then removed. same values.

14.75 compressed, 19.5 extended, 17.375 normal.

Could the panhard rod reduce flex that much? Or is it the HD 6-leafspring pack?

 

based on you numbers I would try to get a shock that extends to about 22" and compresses around 14-15 (as tim mentioned, to prevent bottoming out the shock.) The 22" will allow for more extention. Im not sure what people mean by panhard bar, Ive heard this term many times but not sure what it is. I only know of the tie rods and anti sway bar. If a panhard is the same as anti sway bar then YES it will limit you extension and comprssion a lot. NEVER MIND, just seen you don't have one. Only suggestion I can give is check you schackle bolts that they are not too tight. they should swing as the suspension cycles, if not loosen them a tad. ha, I need to start reading the post dates before I reply.

 

does it have a sway bar? the travel really doesnt sound too far off from normal. the factory springs are always pretty limited

 

If the spring rate is high, typical on early Jeeps of all types, then this could be the issue. These vehicles typically have stiff springs which will cause just what you describe. Early spring technology is definitely not what it is today. Is the panhard rod perfectly level when the vehicle is resting on the ground (full vehicle weight on the springs) or is it angled up or down? If angled it's probably restricting movement somewhat. Might try it disconnected.