4dr Tahoe Leaf Spring Swap (anybody got links/pics?)

[phlegm]

This is my project so far,
1998 Tahoe 4dr LS Build -- GMT400.com Forum
Tires are 265/70R17 (32" tall), they fit but if I ever hit a bump or rut they'd smash into my fender openings.

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My goal is minimal lift, once I get this done I'll determine the best route for the front.

So, without further delay, lets talk about my rear...

Has anybody ever swapped Silverado (64") springs into/onto a OBS 4dr Tahoe (54") ?
I've been looking at online sources for springs
1995-2000 Chevy / GMC Tahoe, Yukon 4 Door 4wd - Leaf Spring (Rear - 4/1 Leaves)
1988-1998 Chevy / GMC C1500 2wd, K1500 4wd - Leaf Spring (Rear - 4/1 Leaves)

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SRI No.	OEM No.	Width	PL-1 SE (A)	PL-1 LE (B)	Arch (C)	No of Leaves	Pack Thck D	Spring Capty.	Remarks
22-795	15620357	2 1/2	32	32	7 3/4	4/1	2 11/16	2,025	Two Stage
22-1151	15707517	2 1/2	27	27	6 1/2	4/1	2 1/8	1,650	Two Stage - 4 Door 4wd

I've been out perusing the forum (there is a LOT to take in) and found the following dimensions thread.
GMT400 Vehicle Dimensions -- GMT400.com Forum
It has a lot of really great information in it.. Like this

GMT400 CrewCab Frame drawing with Dimensions, see how it lists the measurements from the centerline of the axle to both the front spring perch and the rear shackle mount?

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That's really nice, makes it easy to see where the perches are.. (63.32" apart horizontally)

But then it doesn't do the same measurements for the 4dr Utility Body (Tahoe/Yukon)

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Well that's sort of crappy...

Looking at the picture, I can easily move the front mount forward the 5" difference, not a problem.
The rear may be a bit sticky.. without actual drawing measurements I'll have to go out and measure the distance from frame side shackle bolt rearward 5" to see where that puts it in relationship to the body mount and the end of the frame.

I can already tell you that this cannot be a simple matter of moving the stock shackle mount reward, its going to require something custom, the stock shackle orientation (below the spring eye in tension) would run the leaf spring right through the body mount. I had always planned on doing a shackle flip, so that isn't a huge ordeal.

For pickups there are plenty, it isn't rocket science..
Random Ebay Examples for flipped shackles
They generally look like this..

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I do IT for a manufacturing company so I have access to CNC Plasma and Brakes, and professional welders (the men and the equipment) -- I don't weld

This is random pic I took while walking through the shop, It is a bearing pillow block holder, cut/bent/welded by my coworkers.

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I've done smaller projects for other forums that I'm a member of.. (sorry about the brand, but my other serious hobby is working on my '68 Mustang)
Custom SBF motor mounts -- fit most ford unibody -- designed by another forum member

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A 1963 Falcon T5 Crossmember -- again designed by another forum member
Flat Plate, fresh from the Plasma Table

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And Bent -- This was before we got the gooseneck brake dies.

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So before I go reinvent the wheel, has this already been done and documented somewhere or will I be the first crazy ******?

I am not doing this to as a lift kit
Initial thoughts are that I'll have to make a custom frame side bracket designed to get the shackle mounted up as high (close to the body) as possible,
if I have to, I'll make the frame side bracket and if a straight shackle won't work, I'll make a shackle too.. Z-shape or boomerang shape.. whatever it takes to clear the body mount.
And I plan on doing a U-bolt flip.

Other crazy ideas.. if I can't find a suitable spot 5" rearward, I'll consider moving the forward mount 6" toward the front and the rear only 4" back. And then redrill the spring perch 1" offset to maintain vehicle axle centerline. But on the leaf spring would be split 33/31 (F/R). I've seen it done on other forums, its particularly popular with Toyota crowd.

FWIW, I am full of bad ideas...

 

[someotherguy]

If all you're looking for is more load capacity from your springs, you seem to be taking the very hard battle uphill, instead of just looking for upgraded springs that fit your application.

Richard

 

[phlegm]

I don't need load capacity, sure it is a benefit of this. But I'd actually prefer a softer ride not firmer.

Typically for a vehicle you want the softest spring rate possible to achieve desired ride height and the control body roll and jounce with correctly sized sway bars and valves shocks.

No. Im doing it because longer springs ride softer and pickup springs are more common and easy to find.

And because I can.

Same reasons that eventually I'll be swapping out the stock 4dr torsion bar crossmember and bars with 1/2 or 3/4t components.

 

[someotherguy]

OK. Without going over all your engineering drawings and reading the entire post, can you say you've confirmed you have enough rear frame past the centerline of the axle in order to utilize longer springs, as well as confirmed no issues with frame width/design up front in the area you need to relocate the hangers?

Crazier idea maybe? Pull some leafs (something I generally never agree with) to soften it up, then replace load capacity and bounce-resistance with airbags?

Richard

 

[phlegm]

Air ride would be optimal. But the trade off is complexity.

And at this point I'm kind of leaning toward simplicity.
Swap out the electronic shift transfer case for one with a lever. I will never use the 4 auto function of this case. Not to mention the buttons for using it are in a difficult spot to see/use.
Purchase the manual engagement cable for the front axle disconnect.
Even researching Ox lockers.

Back on topic.
The frame forward of the front spring perch is straight, flat, and clear. No worries whatsoever.

The shackle hanger will be the problem.
Over the next few days I'll try to mock some cardboard test brackets.

The splay of leaf springs is what keeps the axle centered (left/right). And by the looks of the ck.pdf. That should be only marginally diminished by using longer springs.

 

[phlegm]

People make spring and shackle brackets all the time, if somebody has done this already, I'd love to skip to the end result.

Its a tad cold here today, supposed to be up into the 30's for the next couple days. Hopefully this weekend I'll get under the 'hoe and mock up some ideas.

For anybody who wants real leaf spring overload...
Leaf Spring Tech -- HotRod.com
and
Shackle Length and Their Impact on Spring Movement -- Quadratec.com
Full of words and pictures like these..

In order to use the advertised spring rate, the shackle should be at 90° to the datum line

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And Shackle swinging has other affects on ride height, a springs natural tendacy is to return to its unstretched/uncompressed state, when the shackle is swinging, this will cause the vehicle to be raised/lowered slightly.

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A common solution is called a shackle slider
These let the shackle bolt move in a linear direction, so you get the actual advertised spring rate without the additional shackle side affects.

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When looking at the diagrams and my actual Tahoe, I've given thoughts to building a set of these instead to be mounted along the bottom of the frame. Could be a simple solution to a packaging problem.

These guys make some commercially
Leaf Spring Slider Kit, Universal - Liquid Iron Industries $149
And they look sexy..

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But with all universal fit parts, they universally require additional fabrication to fit your application.

So we take a look at examples on the web on other 4x4 sites..
new parts delivered, leaf spring sliders/shackle boxes -- Pirate4x4.com
Jeep Tips & Tricks For The Trail -- fourwheeler.com

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school me on leaf spring slider box's -- MarlinCrawler.com

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Being in IT, gives me a LOT of time for online research while waiting for patches or projects and even slow times of the day... I could probably ramble on for days about ways to separate the axle rotation from the leaf spring twist, traction bars, bushing material, spring rate calculators, building spring packs with leaves that are longer in the front and shorter in the rear to achieve ride height and act like traction bars, panhard vs watts, quarter elliptical, using half leaves mounted inverse, shackles of all different types -- revolvers, boomerang, etc.

But I really would like to NOT reinvent this swap if its already been done..