I have restored stock leaf spring pack arch, and added a bit of lift to several saggy stock XJ Cherokee leaf springs. As long as the main leaf is not inverted, an AAL should restore the arch, add some lift, and add some resistance to full load sagging.
As a bonus, AAL ( or a leaf from a used spring pack )are inexpensive, easier to install the full spring packs, and can easily be revered if you don't like the results.
Success with an AAL lift can, and will, depend on the condition of your original leaf pack and with the AAL type used (short overload leaf type or a long full length leaf), and brand name of the AAL. A short overload type AAL has to very stiff to lift the rest of the saggy stock leaves. A severely sagged stock leaf spring will be harder on any AAL than a stock leaf spring pack in decent condition. That is simple physics and plain common sense. I think the first Cherokee AAL kits were the short overload leaf types, and this may be where the bad ride, quickly sagging, Internet mythology stories started. A Short Leaf/overload leaf AAL also concentrates its lift in the area of the original stock main leaf that is already under stress and prone to sagging, near the spring eyes. A Full Length AAL on the other hand, spans between both spring eyes and reduces the weight load each leaf below it has to carry. Spring sag usually begins at the ends of the main leaf near the spring eyes, and progresses to the smaller leaves flattening them out. XJ Cherokee factory original leaf springs are well known to be prone to sagging even with 100% street use. The spring rate or stiffness of a full length AAL will be less than a short AAL. It will ride a little more firmly than stock, but shouldn't be objectionable with good quality shocks.
A point to remember is that no matter what type of lift you use, you are still required to extend your bump stops. Over flexing any leaf spring will cut its lifespan dramatically, no matter what type of lift you install. Leaf springs simply cannot deal with the stress of over-flexing.
Ride stiffness is more dependent on your choice of shock absorbers and the brand name of the lift parts you install, than on the actual type of lift parts, AAL vs brand new lift spring pack. The cheaper brands of lift parts have a tendency to be more stiff riding. All lifted vehicles will ride differently than stock and you should expect some compromises and/or changes in ride quality when driving a lifted Cherokee.
Lift blocks contribute to axle wrap and are the least desirable lift option. Lift blocks are also the most likely lift option to cause excessive leaf spring sagging due to the addition of axle wrap to the lift equation. An AAL does not contribute to axle wrap and will actually help prevent spring wrap.
I have owned or helped my buddies repair or install all types of lift. Our local Cherokee club has 27 lifted rigs and I have owned and built 3 lifted Cherokees and a lifted CJ-7. My XJ started with extended shackles on factory stock leaf packs and so did one of the local XJ's. A 1 week long 4x4 trip proved that the extended shackles will sag and ruin the stock leaf springs very quickly. With a replacement lift spring that is designed to handle the extra flexing and load carrying of an off road trip, extended shackles are just fine and actually help smooth the ride and increase the flex. One of the local XJ's had 2" lift blocks and not only did the leaf spring sag, it went S shaped from axle wrap and then it cracked the main leaf in two. We recently built a bastard pack for another Cherokee using an S-10 spring pack and the original Cherokee Main leaf. This set up works well on the road and trails and gives a little over 4 inches of lift. It gives a smooth ride and reasonable flex on the 4x4 trails. You can vary the lift height achieved by using fewer S-10 leaves or by mixing and matching S-10 and XJ leaves. Another XJ with a 3" AAL and and extra stock Cherokee leaf flexes and rides very well and has not sagged at all.
I ran a Full Length 2.5 " AAL from Rubicon Express on my Cherokee with some un-sagged stock leaf packs along with an extra stock leaf. That netted me a little over 3 inches of lift. I ran this lift on two different week long trips to Moab, a week in the central Colorado Mountains, and regularly hauled 300+ lbs of cargo. It did well on the trails and never sagged in the least in the 3 + years this set up was on my Cherokee. It was maybe 10-15% firmer than stock, but it was smooth on the roads. My current RE 3.5 Replacement Leaf Spring packs are smoother and flex better than the AAL but they also cost much more than the $100 total cost I spent buying and installing the RE 2.5" AAL.
The brand name of products you choose for your lift will have an effect on its lifespan and on the quality/stiffness of the ride, both on or off road. The only way to make lift parts cheaper is to reduce the quality of the materials used to make those parts.
Your lift decision should be based more on your budget, and performance goals, than on any Internet mythology. If your leaf springs are in good condition, an AAL is a reasonable choice to add lift and will meet the needs of most 4x4 users.
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