Some of you may have seen (part of) this in another post earlier this week. Today I crawled under the truck and did some more measuring. I hope this helps somebody in some way......
Leaf spring is app. 60 inches from end to end ( with truck sitting on the ground) and the axle sits on the spring at app. 28" from the front spring eye..The original shackle is 4.5" from center to center--- at least it is on a 2000L.
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I believe part of the problem, is the way some manufacturers name their shackles. Mine were called 2" drop, but the c-to-c distance is actually 3"--which gave me about a 1.5" drop.


Assuming distances over stock:

A '1" ' shackle would move the axle toward the truck frame(lower the truck) .47"

A ' 2" ' shackle would move the axle toward the truck frame(lower the truck) .9"

A ' 3" ' shackle would move the axle toward the truck frame(lower the truck) 1.4"

A 4" shackle would move the axle toward the truck frame(lower the truck) 1.9"

To get an actual 4" drop,you would have to have a shackle that the bolt holes are 8.6" LONGER than the original shackles A '4"- Drop Shackle' is not a '4" Drop' - Shackle.
As I said, mine are 3" over stock, and there is only 1.5" left before the shackle would be rubbing the floor of the bed---so the most you will see is a 4" shackle.

To prove this whole theory, get a 60" 2x4, prop ONE end up 4", and see how much the gap is at 28" from the end.

OK, I'll hush now. (Since Rob 02 covers timing, I'll cover shackles from now on!!!)

 

Speeder just emailed me and said he thinks he may know why I didn't get more than 1 1/2 inches. When we put the shackles on, the truck was half in the driveway and half in the garage. Since the front of the truck was facing down hill, it may have been taking weight off the rear. We are going to try loosening the bolts while the truck is level and then re-tighten. I may even try sitting on the tailgate while he tightens the bolts to ensure there is just a small load on the rear while tightening. Let ya'll know how it turns out.

 

Ummm, I don't think the bolts in the shackle are supposed to be tightened so tight that the shackle can't move back and forth. Isn't it supposed to do that as the spring flexes -- and basically lengthens and shortens?

Is that what you're saying??? Not meaning to argue here....I could be bad wrong.

 

I need the best shackles I can get for my '03.. I want to drop it and level it out...ive seen the pics of people with 3"JLP shackles, and it looks pretty much even...thats exactly what I want...the pics of the DJM 2" shackles on '03's just dont please me. And Mart Man's 4" looks good too. But I really dont see much of a difference between the 3" and the 4". Where can I buy the 3" shackles from? Anybody got em?

 

and a dam fine job your doing

 

I don't want to beat a dead horse but the bolts are to be snug not tight. Sitting on the bed won't make any difference if the shackles are installed correctly.

Like I said before I believe you are comparing apples to oranges with your measurements. The only way to measure a drop is by taking a before and after reading of your truck. Not an after of yours and before of some truck sitting on a lot. The fact that you needed to flip your shims suggests that your drop was significant. However I do believe somehow that you will never be satisfied until you get a meaurement you like. Good luck.

 

You've also got to consider a little geometry/trig here. You're not just raising the axle the same amount as you are the end of the leaf. You're really raising the end through an arc, and the amount the axle moves will be proportional based on it's distance from the either end...

If there were room to put a longer shackle on there it wouldn't take too much more before the shackle would be worthless, because there would be no movement left, because the end of the leaf would be pulled forward by the arc created by the fixed front end point. Not to mention the axle would also sit off center in the wheel opening...

Man I really jumbled that up didn't I. I'm trying to figure out what it says myself...

 

Well, don't know what effect it may have, but this is what we did. Loosened the shackle bolts. I lowered the tailgate and sat on it. Then SPEEDER tightened the bolts. End result. I dropped 1/4" so now the rear is only about 3/8" higher than the front. Ride quality. Better than ever. Suspension seems to have a little less bounce, especially when going over speed bumps, but it's not at all harsh or rigid. As for vibration, there is none. I'm very pleased, and the L looks great. Still not as good as a full front and rear lowering, but way better than before. When I get some good weather and time, I'll get some pics posted. In the meantime, it's going to be this