Leveling Kits (1" to 2")
Teraflex 2" Leveling Kit @ $182. Includes 2" front spacers and 1" rear. Provides clearance for 33" tires and removes the downward rake of the stock front suspension. The disadvantages of this kit are a.) no increase in suspension travel/articulation, and b.) reliance on the OEM springs, which are known to sag as weight is added (i.e., armor, winch).
Entry Level 2.5" Lift (fits 33-35" tires)
Metalcloak 2.5" True Dual Rate Lift Kit with Fox 2.0 Shocks @ $1749. Rock Krawler also has a 2.5" Flex lift for $1435, plus around $600 for a set of Fox 2.0 shocks, but I like the Metalcloak joints and lower price. This will allow you to fit 35" tires with a.) minimal fender flare trimming, b.) replacement flat fenders, or c.) extended bump stops (small reduction in up-travel/flex). 33" tires fit with no caveats. This does not take into account other upgrades that might be needed or recommended to run 35" tires (see bottom of the page). A very complete kit with high quality, low maintenance Duroflex joints provides the best combination of value, on-pavement comfort and up to moderate-level off-road performance in it's price class.
Advanced Level 2.5" - 3.5" Lift (fits up to 37" tires)
Metalcloak 2.5/3.5" Game Changer with Fox 2.0 Shocks @ $2849, or Rock Krawler X-Factor 2.5/3.5 Lift Kit @ 2549 + Rock Krawler Front & Rear Bump Stops @ $140 + Fox 2.0 Shocks @ $565 (Total $3254). The 2.5" version fits up to 35" tires with the same caveats noted above, while the 3.5" version fits 35's with no fender issues or 37's with fender modifications. (Note that 35" is the maximum safe tire size on a non-Rubicon Dana 30 front axle.) The Metalcloak kit is less expensive and includes better flex joints, while the Rock Krawler kit has stronger control arms and track bars.
Lift kits generally do not include steering upgrades; this is considered a separate system. But bigger tires can exert more force on stock components than they were designed to handle, and when rock-crawling, can lead to easily bent components. If you do moderate or above off-roading, I strongly recommend upgrading your ball joints, drag link and tie rod. Even for on-road driving, at 3.5" lift and above, you will need to flip your drag link to attach to the top of the knuckle to reduce bump steer, and this generally requires a new drag link.
There's several good options here. At present, the Teraflex Heavy Duty Adjustable Ball Joints ($260) are the best combination of performance and value. But look for Synergy to come out with their own adjustable BJ's later in 2019.
Drag Link & Tie Rod
At 3.5" lift and above, you will need to flip your drag link to attach at the top of the knuckle to reduce bump-steer. Normally, this means drilling-out the tapered hole in the knuckle with a new taper in the opposite direction, then using a drag link with a 1-ton tie rod end to fit in the larger hole. You might think that buying a heavy-duty tie rod and drag link from your lift manufacturer is a good option. However, often you will pay more and get less than with other third-party options. Steer Smarts has some unique drag link products that allow flipping the drag link without drilling the knuckle, and also incorporates a small shock absorber in the drag link that's said to help reduce bump steer and death wobble. I don't feel the latter should be necessary on a properly set-up steering, but many people swear by it. My preference is for the Barnes4WD JK 1-Ton 7075 Aluminum Flip Steering upgrade kit @ $499. Just be careful because some steering stabilizer/hydro ram clamps might not clear your diff cover with this setup.
4.5"+ Lift Kits
With 4.5" of lift you can fit 37's without fender modification, which is as big as you can safely go on the stock Rubicon axles. While I've heard of people running 4.5" lift on standard "mid-arm" control arms, my feeling is that you'll get better performance both on- and off-road with a long-arm lift. Long-arms produce flatter suspension geometry, which allows greater angles before bushings/joints bind, faster suspension reaction and a smoother ride on- and off-road. While the difference between mid-arms and long-arms are noticeable at 3.5", they really shine at 4.5" and are essential above. My choice is the Clayton Off-Road 4.5" Long Arm Kit for around $3,800. This kit uses a radius long arm front configuration, which some people feel limits cross-articulation. However, it is a relatively simple matter to remove the passenger-side upper radius arm when off-road and run it 3-linked for better flex.
You will need shocks. The Fox 2.0 Adjustable Performance Remote Reservoir Shocks ($1,340) are a long-standing choice for performance and durability. But the Teraflex Falcon 3.3 Piggyback Shocks ($1,472) are gaining popularity. Both of the former offer 12.3" of travel.
Bump Stops and Limiting Straps
You will also need correctly-sized bumpstops (or air bumps) and limiting straps. To measure, you need to fully compress and extend the axle on one side of the Jeep, make sure you're axle and tire aren't making unwanted contact with anything and that the shock isn't fully compressed or extended, then measure how much bump stop is needed. For limiting straps, find suitable mounting points and measure the length required to prevent the shocks from full extension. Spring retaining clips are also a good idea. Prices will vary.
Air Bumps (and Speed Bumps) provide a softer, progressive suspension stop to avoid jarring shock when you bottom out. They are also usually adjustable for height.
Lower Control Arm and Track Bar Mounts
Stock front lower control-arm mounts should be replaced with 1/4" thick mounts, or boxed-in with 1/8" steel plate. Weld-on control arm mini-skids are recommended. These are included in the Artec Axle Armor package recommended below, or available separately for $60.00. Both the upper and lower trackbar mounts should be upgraded or reinforced.
https://www.artecindustries.com/JK_Front_LCA_Mounts https://www.synergymfg.com/synergy-mfg-jeep-jk-front-track-bar-brace.html?category_id=4055 https://www.artecindustries.com/JK_HD_Raised_Trackbar_Front
Sway Bars and Links
Your lift kit will come with extended sway links for the rear. JKS Quicker Disconnects are recommended for the front. Also, rear articulation might be limited by your swaybar, but disconnecting the swaybar can make a rig too unstable on the trails. A Currie anti-rock swaybars can be considered both front and rear, but you do loose some on-road stability on curves with this setup.
As described in the 3.5" lift section, you will need to install a heavy duty tie rod and heavy duty, flipped drag link. In addition, the upper track-bar bracket should be reinforced.
Turning 37's is hard work and, when bound-up on rocks, frequently results in broken sector shafts. A PSC Hydro Assist Kit ($2251, note that there are different kits for 2007-2011 vs 2008-2018) or West Texas Off-Road Redneck Ram ($599) works wonders in beefing-up the steering. But if you stick with the stock steering box, a Sector Shaft Brace (with or without a trackbar reinforcement bracket) should definitely be installed when running 35's or larger and wheeling moderate or harder trails. Other Factors to Consider With 35" or Larger Tires
The stock Dana 30 in non-Rubicon models cannot safely run 37's on most off-road terrain. The Rubicon's stock Dana 44 can safely go up to 37" tires.
You may need to regear your differentials. If you have a 3.8L/Auto you definitely will want to regear for 35's. A 3.8L with a stick will probably want to regear for 35's. A 3.6L will be slower off the line, but otherwise might be bearable up to 37's. Which gear ratio to pick depends on your engine, transmission, tire size and driving style.
You will need new wheels with 4.5" or less backspacing, or 1.5" wheel spacers, to avoid rubbing with 35"-37" tires. I'm not a fan of spacers, and they are illegal in some states.
Axle reinforcement is strongly recommended for 35"+ tires. Adding Inner C-Knuckle Gussets ($80 plus welding) and either Sleeving ($96 plus welding) the axle or installing a Truss will help avoid bending and breakage. My preference is for the Artec JK Dana 44 Axle Armor Kit, ($319 plus welding) which includes a truss, c-gussets, upgraded trackbar bracket and lower control arm skids.
Chromolly axle shafts are recommended if you do moderate difficulty or above trails. In particular, the stock rear axle shaft flanges are known to bend easily.
At and above 2.5" of lift there is a chance the Rzeppa CV joint on the front (2-door and 4-door) and rear (2-door) driveshafts will fail quickly. At 3.5" the front driveshaft on all JK's, and rear driveshaft on a 2-door, should outright be replaced immediately. Adams, Carolina Driveline, J.E. Reel and Tom Woods are reliable brands. But you may be able to get a perfectly good driveshaft from a local driveline manufacturer for the same price or less, and benefit from local service if your driveshaft ever needs repairs.
Finally, the stock brakes may not be sufficient to safely stop a JK on 35's, and are definitely poor for 37's. A Mopar J8 Brake Booster and Master Cylinder ($269) will provide more fluid to the calipers for higher clamping force. Then either go with upgraded pads and rotors, such as Powerstop Z36. Or upgrade to Crown Front Big Brakes ($480) and G2 Rear Big Brakes ($464) for a huge improvement in braking power.
As you can see, there's a lot of additional parts and cost involved as you progress from 2.5" to 3.5", and more so to properly run 4.5" or more lift. Can you skimp on things like axle reinforcement or steering upgrades? Perhaps, but my philosophy is to provide the best advice possible to support off-roading at the level implied by the tire size while still maintaining a safe and comfortable ride on the highway. The kits recommended are generally the most affordable in their class with due consideration to these parameters. It is really surprising to me that so many JK owners go with kits such as Rough Country or Zone Offroad because of the price, when the price of a superior kit from Metalcloak (or Rock Krawler) is within $100 dollars or so (often cheaper).
If you want to keep things "cheap," the best thing you can do is install the minimum amount of lift necessary for your tire size, and either trim the factor fender flares or replace them with tube fenders from Crawler Concepts, Metalcloak, Poison Spyder or one of many other vendors.