Dude... hand me the BFH.

Leaf Spring Overhaul

May 24th, 2009 Posted in Rear Suspension, Tech

When we got this Jeep, it had some sort of lift on it. It looked like a 3.5″ lift kit that had settled quite a bit. The good part was that the leaf springs didn’t look abused at all; the bushings were in good shape, and the leaves were nice and flat. We figured that if we could make that leaf pack work, it would give us a nice ride and a good amount of flex.

We did need a bit more lift though, so we picked up a main leaf from a Rubicon Express lift pack from a friend of ours. The leaf pack it came from was for a 3.5″ Cherokee lift. It was pretty well broken in, but we hoped it would get us an extra inch or two when we added it into our pack.

When I took our springs apart, we discovered that, although it was an aftermarket leaf pack of some sort, it also had a full length Rubicon Express add-a-leaf installed in it. I figured I would put the cut-down main leaf right under the existing add-a-leaf.

Since I had to take the leaves apart anyway, I decided to do a full overhaul. I started by enlarging the hole for the center pin from 5/16″ to 3/8″.

(Cutting oil and sharp bits are your friends.)

I also drilled a few 3/16″ holes for spring clamps. (More on that later.)

Next, I needed to cut the ends off the main leaf we picked up.

Leaf springs are tempered steel, do not cut them with a torch or plasma cutter or you will ruin the spring!

Then I cleaned up the end with a flap wheel to prevent the sharp edges from gouging the other leaves.

When that was done I cleaned up all the leaves with a wire wheel…

and wiped them down real well with brake parts cleaner.

After all the grease, and dirt, and rust, and cutting oil was removed, it was time for our secret weapon:

Graphite spray lubricant (sometimes called “graphite paint”) is primarily used to lubricate farm equipment when grease would just act as a magnet for dirt and debris. It sprays on just like paint (hence the ‘AKA’) and does a pretty good job of reducing the friction between metal parts.

I laid all the leaf springs out and applied three, moderately thin coats of the graphite spray.

Then I turned them over and did the same thing to the other side. I didn’t paint the top side of the main leaf or the bottom side of the overload leaf though. It took about a can and a half to do both packs.

The next upgrade in our leaf pack overhaul was a Teflon leaf spring liner we ordered from Eaton Spring. It’s basically a thin, 2.5″ wide, piece of Teflon with short edges to keep it centered under the springs.

The spring liner gets installed between all the leaves. I stacked everything from the overload leaf to the main leaf with the pack upside down.

They liner will straighten out once the weight of the rig is on it for a few hours. There is no need to reinstall the plastic pads that used to be on the ends of the leaf springs. The Teflon liner takes the place of them.

I trimmed some of the excess off, but some will have to be trimmed after the leaf packs are installed.

(Try not to cut your finger off.)

After getting the leaf packs back together, I gave them a coat of semi gloss black paint. The graphite spray will (slowly) wipe off on your hands and doesn’t look as nice.

The final step in this makeover is fabbing some some leaf spring clamps that are less restrictive than the ones Rubicon Express sells.

I started by cutting some 1″ x 1/8″ steel strap into 12″ sections. I drilled a 3/16″ hole in the center of each of them as well as in a small scrap of 1/4″ steel that was exactly 2.5″ wide.

I then lined up the holes on one of the 1″ wide pieces and the 2.5″ wide scrap and then held them together in the vice.

This allowed me to bend the strap at a 90° angle and keep the width exactly what I needed. I used another 1/4″ thick scrap on the other side to keep the back supported. Then I just gave it a few taps with the BFH.

Next up was drilling a hole for the bolt to go through. I put the clamps around the spring pack and picked an arbitrary place for the holes. I figured, if the clamps allow the springs to open up too much, I can drill another hole lower, or put some kind of bushing around the bolt, between the sides of the clamp.

The hard work was done… time for paint.

Remember that 3/16 hole we drilled earlier for the spring clamp? Something needs to keep the clamps affixed to the lowest spring, so that they don’t end up down by the spring perch. Some people have used countersunk bolts, but the leaf manufacturers use rivets, so that’s what we’re using. The rivets need to be inserted from the top, first through the leaf, and then through the clamp, which meant that we had to disassemble our leaf pack again. Better planning could have prevented this.

I used nylock nuts on the bolts that go through the leaf clamps. This way, the leaf clamps could be somewhat loose but the nut still won’t back off. This clamp design will allow the springs to open up (flex), but it will still prevent the leaves from fanning out.

You want as many leaves as possible to be contained by the clamp, but the clamps need to be somewhat close to the spring eyes to keep the leaf packs from opening up too far.

Here you can see the position of the clamps. This will vary depending on your leaf pack.


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