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Front Leaf Spring Conversion
Swapping the XJ front suspension from 4-link coil to Spring Over Axle Leaf springs



Intro

The first question people always ask is "why?".

Well, the first 3 pictures should explain how unsatisfactory the stock setup was when I reached about 7" of lift. The control arm angles were way too steep, the steering was way beyond its design limits, and the ride and handling sucked....and I wanted to go bigger yet. So what to do? I could have done a custom multi-link design or one of the so-called "long arm" conversions....but that's a lot of trial and error and geometry to make it all work well. So I chose the simple, proven reliability and performance of the leaf spring over axle setup. I just love the clean simplicity and the ease of fine tuning the lift height and wheelbase.

stockproblems1small.jpg

Scary stock steering angles.

stockproblems2small.jpg

Gross control arm angles, and these were already custom adjustable-length control arms.

stockproblems3small.jpg

The ugly truth behind the rubber boots.

leafspring1small.jpg

I basically set about emulating the simple YJ design, but spring over axle (SOA).

leafspring2small.jpg

SOA has worked extremely well for the short wheelbase guys for years.

leafspring3small.jpg

And I had access to free YJ front springs (thanks Chad!).

leafspring4small.jpg

leafspring5small.jpg


The next few pics show the initial step of cutting off the XJ coil bracketry.

leafspring6small.jpg

This was my first time with the ol' flame wrench (thanks to Rico for hauling his out here for me).

leafspring7small.jpg

leafspring8small.jpg


I made an ugly job of it, but as Chad keeps saying..."you're not building a space shuttle) :)

leafspring9small.jpg

leafspring10small.jpg

leafspring11small.jpg


Because of the required location (to centre the axle) for the driver's spring perch, the diff housing requires some modification.

leafspring12small.jpg

The inner U-bolt on the driver's side needs to fit around the stub on the diff housing.

leafspring13small.jpg

All the coil brackets removed.

leafspring14small.jpg


The inner U-bolt on the passenger side fits around the large disconnect housing, which needs a little "cleaning up". If you're working with a non-disconnect housing, this won't be an issue. Personally I like the strength of the big cast disco housing.

leafspring15small.jpg

Driver's spring perch mock-up.

leafspring16small.jpg

Passenger side spring perch mock-up.

leafspring17small.jpg

leafspring18small.jpg


The required placement of the spring perches requires 2 different diameters. Good job I was making them myself.

leafspring19small.jpg


3 different size U-bolts were required, as follows:

2.5" - Passenger and Driver side outer
3" - Passenger inner (to fit around disco housing)
3.25" - Drivers inner, to fit around diff housing

U-bolt plates are just 1/4" steel plate.

leafspring20small.jpg


This is how the perches will sit to centre the axle under the Jeep. To figure out the locations, here's what I did. Mounted the rear of the leaf packs in the stock LCA frame brackets. Measured diagonally between them to get them parallel to one another and the frame. With them in this orientation, measured the width between the centring pins of the leaf packs (dimension A). I then measured the width of the axle from inner knuckle to inner knuckle (dimension B). Subtract A from B, result is C. Divide C by 2, result is D. Measure from inner knuckle (same location as used in getting dimension B) in an amount equal to D. This is where the centre of the new spring perch needs to be.

leafspring21small.jpg

Initial mock-up of leaf spring location.

leafspring22small.jpg

This is how I measured between the centre pins of the spring packs.

leafspring23small.jpg

Showing where front will mount.

I did not want to do a shackle reversal because I didn't want to buy a new "high travel" front drive shaft, and according to my research, it would be of little or no benefit, and could even be counter-productive. Check out John Nutter's excellent article on the subject at www.jeepwire.com.

leafspring24small.jpg


I was fortunate enough to have a big sturdy custom bumper of 1/4" plate to mount my shackle hangers to. It would be very simple to make a cross member though.

leafspring25small.jpg

My bumper attaches with many bolts.

leafspring26small.jpg


I chose to mount the rear of the leaf packs in the stock LCA frame brackets. They were already there, in the right place, and the right width for the spring eye bushings.

leafspring27small.jpg


Like the pic says, I drilled a new hole in the LCA bracket, 1.5" behind the stock hole, so the wheelbase would come out stock.

leafspring28small.jpg

Here's the axle installed for the first time.

leafspring29small.jpg


leafspring30small.jpg

Pic with many labels :)

leafspring31small.jpg


This pic shows how I accomplished moving the axle back 5" (from where it would have been if I'd made no adjustments) so the wheelbase would remain stock. Later, I would end up re-using the centred spring perch hole, as opposed to the offset one I drilled, moving the axle forward about 1.75" to keep my 36" Swampers off the back of the front fender wells.

Note the inner knuckles are swapped on CJ units as part of my hybrid axle with manual hubs project - detailed elsewhere on my site.

leafspring32small.jpg


Here you can see 2 initial concerns I had:

1) I placed the front shackle hangers a bit too far forward, leaving the shackles almost vertical, where I would have preferred a steeper angle to the shackle (bottom of shackle further forward than top) so there's no chance it would fold back on itself against the frame and bend the spring. This has turned out not to be a problem at all.

2) I was concerned about the stress of the short AAL on the spring pack. In the end, I fine tuned the leaf pack by removing the shortest stock lower leaf, and adding 2 long leafs, one almost full length. The short AAL is also still present (1 year later) and isn't a problem. I love how easy it is to fine-tune a leaf spring suspension.

leafspring33small.jpg


I did use the passenger side UCA axle bracket and bushing as a track bar mount initially, but have since removed the track bar and sway bar and am perfectly happy with the results. My shocks are RS9000 set on stiffest setting on the street.

leafspring34small.jpg


Despite my concern (when I labelled the pic) the shackle position has been fine, and the leafs have been customized to where they are equal and even.

leafspring35small.jpg


I think I was a little too hard on myself when I did up these pictures initially. It has all worked out exceptionally well - and to see it in action, check my "action" page:

leafspring36small.jpg


I think.....

leafspring37small.jpg


.......Leaf springs........

leafspring38small.jpg


.........Rock!!


Summary:

If you're going to do this yourself, you will have to work out the steering on your own. As I customized my axle (D44 outers) at the same time, I used D44 flat top knuckles and built a custom Hy Steer crossover steering while I was at it. Articles are on my site elsewhere. If you're keeping the stock knuckles, you will have to work it out yourself. I imagine there may be problems with the drag link hitting the passenger leaf pack. Good luck !


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Front Leaf Spring Conversion
Swapping the XJ front suspension from 4-link coil to Spring Over Axle Leaf springs



Intro


The first question people always ask is "why?".

Well, the first 3 pictures should explain how unsatisfactory the stock setup was when I reached about 7" of lift. The control arm angles were way too steep, the steering was way beyond its design limits, and the ride and handling sucked....and I wanted to go bigger yet. So what to do? I could have done a custom multi-link design or one of the so-called "long arm" conversions....but that's a lot of trial and error and geometry to make it all work well. So I chose the simple, proven reliability and performance of the leaf spring over axle setup. I just love the clean simplicity and the ease of fine tuning the lift height and wheelbase.

View attachment 3075063
Scary stock steering angles.

View attachment 3075064
Gross control arm angles, and these were already custom adjustable-length control arms.

View attachment 3075065
The ugly truth behind the rubber boots.

View attachment 3075066
I basically set about emulating the simple YJ design, but spring over axle (SOA).

View attachment 3075067
SOA has worked extremely well for the short wheelbase guys for years.

View attachment 3075068
And I had access to free YJ front springs (thanks Chad!).

View attachment 3075069
View attachment 3075070

The next few pics show the initial step of cutting off the XJ coil bracketry.

View attachment 3075071
This was my first time with the ol' flame wrench (thanks to Rico for hauling his out here for me).

View attachment 3075072
View attachment 3075073

I made an ugly job of it, but as Chad keeps saying..."you're not building a space shuttle) :)

View attachment 3075074
View attachment 3075075
View attachment 3075076

Because of the required location (to centre the axle) for the driver's spring perch, the diff housing requires some modification.

View attachment 3075077
The inner U-bolt on the driver's side needs to fit around the stub on the diff housing.

View attachment 3075078
All the coil brackets removed.

View attachment 3075079

The inner U-bolt on the passenger side fits around the large disconnect housing, which needs a little "cleaning up". If you're working with a non-disconnect housing, this won't be an issue. Personally I like the strength of the big cast disco housing.

View attachment 3075080
Driver's spring perch mock-up.

View attachment 3075081
Passenger side spring perch mock-up.

View attachment 3075082
View attachment 3075083

The required placement of the spring perches requires 2 different diameters. Good job I was making them myself.

View attachment 3075084

3 different size U-bolts were required, as follows:

2.5" - Passenger and Driver side outer
3" - Passenger inner (to fit around disco housing)
3.25" - Drivers inner, to fit around diff housing

U-bolt plates are just 1/4" steel plate.

View attachment 3075085

This is how the perches will sit to centre the axle under the Jeep. To figure out the locations, here's what I did. Mounted the rear of the leaf packs in the stock LCA frame brackets. Measured diagonally between them to get them parallel to one another and the frame. With them in this orientation, measured the width between the centring pins of the leaf packs (dimension A). I then measured the width of the axle from inner knuckle to inner knuckle (dimension B). Subtract A from B, result is C. Divide C by 2, result is D. Measure from inner knuckle (same location as used in getting dimension B) in an amount equal to D. This is where the centre of the new spring perch needs to be.

View attachment 3075086
Initial mock-up of leaf spring location.

View attachment 3075087
This is how I measured between the centre pins of the spring packs.

View attachment 3075088
Showing where front will mount.

I did not want to do a shackle reversal because I didn't want to buy a new "high travel" front drive shaft, and according to my research, it would be of little or no benefit, and could even be counter-productive. Check out John Nutter's excellent article on the subject at www.jeepwire.com.

View attachment 3075089

I was fortunate enough to have a big sturdy custom bumper of 1/4" plate to mount my shackle hangers to. It would be very simple to make a cross member though.

View attachment 3075090
My bumper attaches with many bolts.

View attachment 3075091

I chose to mount the rear of the leaf packs in the stock LCA frame brackets. They were already there, in the right place, and the right width for the spring eye bushings.

View attachment 3075092

Like the pic says, I drilled a new hole in the LCA bracket, 1.5" behind the stock hole, so the wheelbase would come out stock.

View attachment 3075093
Here's the axle installed for the first time.

View attachment 3075094

View attachment 3075095
Pic with many labels :)

View attachment 3075096

This pic shows how I accomplished moving the axle back 5" (from where it would have been if I'd made no adjustments) so the wheelbase would remain stock. Later, I would end up re-using the centred spring perch hole, as opposed to the offset one I drilled, moving the axle forward about 1.75" to keep my 36" Swampers off the back of the front fender wells.

Note the inner knuckles are swapped on CJ units as part of my hybrid axle with manual hubs project - detailed elsewhere on my site.

View attachment 3075097

Here you can see 2 initial concerns I had:

1) I placed the front shackle hangers a bit too far forward, leaving the shackles almost vertical, where I would have preferred a steeper angle to the shackle (bottom of shackle further forward than top) so there's no chance it would fold back on itself against the frame and bend the spring. This has turned out not to be a problem at all.

2) I was concerned about the stress of the short AAL on the spring pack. In the end, I fine tuned the leaf pack by removing the shortest stock lower leaf, and adding 2 long leafs, one almost full length. The short AAL is also still present (1 year later) and isn't a problem. I love how easy it is to fine-tune a leaf spring suspension.

View attachment 3075098

I did use the passenger side UCA axle bracket and bushing as a track bar mount initially, but have since removed the track bar and sway bar and am perfectly happy with the results. My shocks are RS9000 set on stiffest setting on the street.

View attachment 3075099

Despite my concern (when I labelled the pic) the shackle position has been fine, and the leafs have been customized to where they are equal and even.

View attachment 3075100

I think I was a little too hard on myself when I did up these pictures initially. It has all worked out exceptionally well - and to see it in action, check my "action" page:

View attachment 3075101

I think.....

View attachment 3075102

.......Leaf springs........

View attachment 3075103

.........Rock!!


Summary:

If you're going to do this yourself, you will have to work out the steering on your own. As I customized my axle (D44 outers) at the same time, I used D44 flat top knuckles and built a custom Hy Steer crossover steering while I was at it. Articles are on my site elsewhere. If you're keeping the stock knuckles, you will have to work it out yourself. I imagine there may be problems with the drag link hitting the passenger leaf pack. Good luck !


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Awesome write up. I'm using your experience as a guide. Thanks!
 
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