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SkinnyG 06-01-2012 06:56 PM

2WD leafs, 4WD leafs, & something in-between
Inspired by this thread here: Made my own leaf spring pack... FRANKEN-LEAFS!

Coles' Notes: Don't do this. It's a lot of work; 4-link & coilovers or bags would be much, much better.

A while back I looked into running 4WD leafs. They have less arc, thicker leaves, and it looked like it could work.
4WD leaf pack on top, 2WD leaf pack (with 3", 5 tapered block) on bottom.

They DON'T work - the center pin is about 1-1/2" further forward on the 4WD leafs, and your driveshaft doesn't have that kind of range.

Then I got to thinking. Maybe I could de-arc the 2wd leaf, add the thicker 4wd second leaf, use the 4wd overloads which are arced the correct way....

Based on the packs I measured:

2WD main leaf: 0.282"
4WD main leaf: 0.282"

2WD second leaf: 0.282"
4WD second leaf: 0.319" (by my calculations, 50% stiffer than the 2WD leaf)

4WD overloads are longer and thicker, but I did not measure them.

So, to get started, I pulled the leaves out.

And disassembled both 2wd and 4wd sets of leafs.

2WD overloads (top) vs 4WD overloads (bottom). This is a Canadian model, so your leaf pack might be different.

I de-arced the 2wd main leaf by first marking 1" increments along the entire length, and then drawing the existing arc on the table as a reference.

I measured the existing height, and made a mark 3" lower.

This is my crazy device for re-arcing leaves. The threaded bolt is a stop to ensure a consistent bend at each 1" point.

Bending. This takes some trial and error, but the system works once you get it going.

I reassembled the leaf pack with 2wd main, 4wd everything else.

Here it is installed with a 6 shim. The rear shackle doesn't look happy, and may need to be relocated.


It's different. Less axle wrap. It's stiffer for sure, maybe 25% by my butt-dyno. It bottoms ~really~ nice - you can tell the springs get progressively stiffer (hitting the overload).

The driveshaft ended up placed where it's supposed to be (the blocks and the angle previously stuffed the driveshaft way into the transmission), so my "shortened" driveshaft was now too short (good thing I had the original).

I'll post back with some long-term evaluation later.

1989D21 06-02-2012 05:16 AM

Nice work! I'd be interested to see what your solution is for that rear shackle though.

Vegeta_SS4 06-02-2012 02:21 PM

I like your do it yourself engineering and your trail and error method of testing. Some times you just gotta try it to see if it will work . Thats the only way to know for sure. Great job man!

SkinnyG 06-05-2012 03:41 AM

So, this is bad, ok:

That shackle isn't really doing anything - the spring cannot do its job at all. So, either I need to (A) add some more arc, (which would require going back to blocks), or I need to (B) relocate the leaf spring shackle.

I took a weekend to think about it, and decided (B) made the best sense.

So, out came Mr. Plasma Cutter.

And off came the brackets, trimmed back of course, to be welded back onto the frame brackets.

That's not my poo weld, really it isn't.

Done, and move on with my life.

1989D21 06-05-2012 03:49 AM

Very nice... How's the ride? And what's all the stuff on your bushings? Grease?

SkinnyG 06-05-2012 03:59 AM

The ride is a slightly stiffer than the stock leaf pack.

The axle-wrap is not felt, and acceleration on a bumpy corner does not have anywhere near the wheel hop that it did with 3" blocks.

The ride feels "correct" vs. the messed up shackles. When the shackles were messed, it felt ok if it wasn't bumpy, but "wrong" if it was - and it was hard to put your finger on exactly what was going wrong, but it felt wrong.

I didn't add any arc back into the springs, so it (seems) to still be hitting the overloads near full bump. I think. Debating whether to change that (by either adding some arc, or by adding some arc to the overloads a bit), or just leave it.

Shackle is touching the tailpipes now. It just doesn't stop, doesn't it?

SkinnyG 06-05-2012 04:01 AM

The grease is molybdenum disulphide - great for polyurethane bushings (which these are).

1989D21 06-05-2012 04:23 AM


Originally Posted by SkinnyG (Post 280960)
The grease is molybdenum disulphide - great for polyurethane bushings (which these are).

Great info, thanks!

SkinnyG 06-21-2012 04:45 AM


I noticed that there was a metallic "clank" at every bump. Turned out the overload leafs were about 1/16" away from the main leafs, and would slap each other. Not good.

So, I arbitrarily figured maybe an inch of clearance should be good. The larger overload had 1-1/2" of free arc to it. I took it out and re-arced it to 2-1/4", and re-arced the second overload (not applicable to US models)to fit.
Increased overload arc top, factory overload arc bottom.

This turned out to be even worse. I was surprised to find out just how much the overloads contribute to every day driving. Arced like this, the truck was a wallowing, floating pig. It was awful.

I lasted two days and pulled the leafs out again.

I cut the ends of the currently unused 2wd 2nd leaf and arced it to match the leaf pack, un-arced the overloads back to 1-1/2" free arc, and fab'd a simple 1/2" spacer to (hopefully) account for the added leaf.
Newly molested 3-leaf pack in foreground.

The leaf pack now sits pretty straight on the truck (which is good), but the overloads are not being utilized (which is bad). So...... I am going to try the flipping the 2wd overloads and installing them instead, as they have even less arc, and are thinner (which might behave a bit better). We'll see....

1989D21 06-21-2012 04:51 AM

Good luck!

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