Post mount (1975) wagoneer shackle flip lift height?

Cataldo · Post by **Cataldo** » Thu Apr 23, 2015 6:29 am

Hello,

I have tried to find out through searching but have not found my answer. How much lift does a shackle flip on a post mount '75 wagoneer net? Obviously spring condition plays into effect, looking for a rough answer. I figure 2-3". Rather not assume anything though. Pinion angle then needs to be corrected with shims after this as well. What are the negatives to a shackle flip? Rougher ride?

Thank you.

SJTD · Post by **SJTD** » Thu Apr 23, 2015 6:47 am

Since the axle is roughly in the center of the spring the lift is roughly half of what the rear of the spring drops. So you get lift equal to the length of the shackle itself. If the axle is forward of the center of the spring it will be less.

A simple Geometry problem. You remember Geometry don't you? Or is it Trig?

Cataldo · Post by **Cataldo** » Thu Apr 23, 2015 7:48 am

Correct. Unfortunately I do not have a fsj quite yet, picking it up tomorrow. Just curious and getting ahead of myself.

tgreese · Post by **tgreese** » Thu Apr 23, 2015 8:29 am

Trigonometry is sines and cosines and their ilk. Geometry is about shapes and figures, like triangles, the conic sections, rectangular figures, and so forth. You can use trigonometry to explore and describe geometry.

Post by **Stuka** » Thu Apr 23, 2015 8:59 am

I got about 2.5" out of mine. I think Tad got roughly the same. It does point the pinion up a lot, so shims to lower it are needed. It also moves the axle forward some.

The ride is rougher because of the poor shackle angle. Its pointing forward, which means the rear eye of the spring has to move down in order for the spring to compress up.

But it is a quick job. Unbolt rear eye, get some giant pliers to rotate the shackle (they are always frozen in place), bolt back up.

SJTD · Post by **SJTD** » Thu Apr 23, 2015 11:23 am

So using Trigonometry you can compute the change in the Geometry of the suspension. Wait, change? Doesn't that require the Calculus?

Cataldo · Post by **Cataldo** » Thu Apr 23, 2015 4:27 pm

Thanks, 2.5" is right on par with what I was figuring.

I wonder what is a better set up, a 2" lift spring that has a greater eyelet to eyelet distance to 'fix' the shackle angle or leave the shackle orientation stock and run a 4" leaf. Mostly just thinking out loud on this one.

Post by **Stuka** » Fri Apr 24, 2015 8:21 am

You really cannot run lift springs with the shackle flipped. It pushes the axle quite a ways forward. I did run some blacks in back (backwards) and it was ok, but not ideal. Back then there was no lift springs for post mount rigs. Now there is. If you can afford springs, go that route.

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Cataldo · Post by **Cataldo** » Sat Apr 25, 2015 8:28 am

Yeah I'll be going to new springs eventually. I'm thinking of going with hell creek 4" lift. Probably just their Springs and work out everything else locally.

carnuck · Post by **carnuck** » Mon Apr 27, 2015 9:02 am

The lift should be the amount of the shackle pin center to pin center because you are doubling that distance when you flip (not accounting for spring sag). If there is a shop where you can do the flip that has an engine hoist and floor anchors you can do it with a comealong without removing the shackles.

This was what I did to my '73 J4000.
First, make sure the rear brake hose is long enough (mine was). (I left the tires on)
Undo the shocks (I did the bottoms) and check Ebrake cable length (I just undid mine).
Anchor a chain from the floor to the axle (both sides to make it even is best) then attach the engine hoist to the rear frame under the bumper (Not the axle or it defeats the purpose. Not the bumper or it may go flying off!) with a 4x4 under the bumper and across the frame to "cradle" it like tow trucks do.
Lift until the rear springs are pulled downwards almost flat.
I used a prybar to complete the downward flip of the shackle and a comealong attached from the shackle to the engine hoist to pull it back until it went over center.

The combined weight of the axle and chains pulling down kept the flip from being "violent". I left the comealongs "snug" on the now flipped shackles and lowered the truck down. I had to move the truck in a hurry, so I hooked the bottom of the shocks back on and pulled out. (took me 2 hours, but I'm an ex-tech and did as much as I could ahead of time)

In hindsight, angle shims would have been better, but it rarely saw the road empty so the angle didn't get to knocking point very often.

Tad · Post by **Tad** » Thu Apr 30, 2015 4:20 am

Stuka wrote:I got about 2.5" out of mine. I think Tad got roughly the same. It does point the pinion up a lot, so shims to lower it are needed. It also moves the axle forward some.

The ride is rougher because of the poor shackle angle. Its pointing forward, which means the rear eye of the spring has to move down in order for the spring to compress up.

But it is a quick job. Unbolt rear eye, get some giant pliers to rotate the shackle (they are always frozen in place), bolt back up.

This is correct.
The stiffer the springs the more pronounced the pinion angle, wheel move and shackle angle will be.
It was a harsh ride but it settled into place over time.
I drove like that from 2002 until 2006 when I took all that post mount crap off and went SOA up front with a real shackle flip in the rear.

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