Leaf Springs in rear of TJ

[toyrunner95]

i dont know much about jeeps, but im learning. the coil springs in the rear i feel will be much more capable than any leafs, however, since you arent dealing with steering it may not be such an influence. i think that you could get away with airbags and coils if you try. perhaps if you put them on the links or just inside the coils.

a leaf swap is fairly simple, u can also clock the rear housing if you have a lift. OR get a YJ rear and swap over the diff. should be a streight swap, maybe.

 

[goodtimes]

If weight is the big issue (sagging springs), simply get springs with the proper rate. Find out how heavy each end of your jeep is, and compare that to the numbers from a stock jeep. If the rear weighs 400 pounds more than stock, you'll want springs that will support 400 pounds more than the stock springs did. It may not be an "off the shelf" spring (or you might get lucky--you'd have to call around and see) , but I'm sure there are places making coil springs to customer specs, just like they make leafs to customer specs....

 

[DakarTJ]

I ran tour Jeep in Sedona for a wile. We could put 6-8 people in the back of one. We used RE coil springs and put the air bags in the coil. The key to make the bags work was, the ability to set individual bag presser. With this set up is could adjust for off camber hills or loads. We pumped up the bags for the tarmac and let some of the air out for the trail.

 

[4Rescue]

the JK swap is for the ultimate adventure, its actually a dodge chassy under a jeep jk.

yeah there was that, but what I'm talking about was a new system for the JK that runs Leafs... And of course I can't find that article anywhere now...

 

[madizell]

I can't imagine why anyone would want to undergo the effort of changing from coils to leaf springs. Both are intended to hold up the back of the car, and both do that. Coils necessarily require some form of axle location control, whereas leaf springs perform both functions (load and location). However, the best leaf springs don't react as quickly as your average coil spring, and almost without exception, cannot be made to provide the same degree of axle travel that simple coils can provide. Leaf springs contain more mass, which requires more effort to move around. They do best where load control is your primary focus. If ride quality, articulation, adaptability, tractability, and pure off road function are your principal concerns, coils are better by far. If you have a coil rear and don't like the trac bar, buy or build a 4-link to replace the 3-link.

 

[OS-Aussie]

Superlift have rear leaf springs in their X2 lift kit. There is some suggestion that this may create more stability in the vehicle. One of the guys at Expert off-road has leaf springs on his LJ and loves it. But then again he owned a CJ7 prior to this.

Coils in the front and leaf springs in the rear has been around for ages in many brands, mostly to address heavier loads.

 

[prepmech]

A friend of mine is just finishing up putting some XJ springs on the rear of his YJ. He used the stock YJ front spring hangars, and some Ruffstuff way-back shackle hangers in the rear. He gained about 6" of wheelbase, and comp cut the quarter panels to allow the tires to stuff. He also had to remove the fuel tank and add a fuel cell to allow the axle to fit that far back. He is running the stock XJ springs over the axle in the rear, and stock YJ springs over the axle in the front. It flexes really well, but he still has some issues to work out with his shackles. He is also having to add a traction bar as he is having some axle wrap problems with the long side of the spring in front of the axle.

Another friend of mine is going to be doing the same to his TJ, he says the XJ springs will mount in the stock TJ lower control arm brackets.

The XJ springs are great for a trail rig, but not so much for an expedition rig because of the issues with cutting the body and moving the fuel tank.

 

[IXNAYXJ]

However, the best leaf springs don't react as quickly as your average coil spring, and almost without exception, cannot be made to provide the same degree of axle travel that simple coils can provide.

We're not talking about a comp crawler, but an expedition type rig. A 1200 RTI score is not necessary, and leafs flex just fine for that matter.

The advantage as I see it to the leafs is the added stability and predictability. Leafs don't "unload" as rapidly as coils and offer a built in "sway bar" effect, if you will. Side hills would be a lot less scary.

Further, the rig in question will be doing a lot of trailering, and with the weight of gear inside and the tongue weight, the leafs make sense to me.

To answer your other question about "who would want leafs," that would be Chrysler. The Egyptian Military version of the JK (the J8) and the new JT both switch over to a leaf sprung rear suspension. A lot of rigs over the years have used coil front/leaf rear to great effect, most notably the Jeep XJ Cherokee and Ford Early Broncos.

Also, as the rig Frank's talking about is going to be something of an advertising/show piece, the leafs would be a cool thing for people to look at and say "oooh!"

-----Matt-----

 

[madizell]

I wasn't referring to rock crawling. Traveling on washboard roads is something that lots of expedition folks will do, and for this, coils are better because of the cyclic rate capability of the coils. Also, crossing the odd creek crossing will sometimes require a bit of suspension flex. Coils provide better use of available articulation. Just my opinion, of course, but if the vehicle already has coils on it, it is easier and cheaper to build up the coil suspension to perform as you wish than to completely replace the rear suspension with leaf spring, especially where anything you attempt will be pure custom work, with all of the engineering problems yours to solve.

 

[madizell]

The advantage as I see it to the leafs is the added stability and predictability. Leafs don't "unload" as rapidly as coils and offer a built in "sway bar" effect, if you will. Side hills would be a lot less scary.



-----Matt-----

The tendency for leafs to unload more slowly is exactly what I was referring to regarding cycle rate. As for being more stable because of this effect, my experience suggests you are mistaken. With leaf springs at all four corners, I still needed sway bars front and rear to control body sway in off camber and side hill situations, not to mention just driving down the road. Following a full coil TJ into rough terrain, I managed to tip my CJ over, leaf springs and all, following the exact same route with a nearly identical load and lift. There is far more to the question of stability than merely what kind of spring is used.

 

[highlandercj-7]

Several people I know round here have done it. First is a guy that put them in the front. Waggy lift springs. Second same guy with a set of xj rear lift springs this streched the wheel base and added stability, and third a guy that put leafs all the way around on a LJ.

Still trying to find the rear leaf sprung jeep......