That depends on if you get a YJ or a TJ. But, for anything 3" or higher, the following items are recommended to avoid mechanical problems mostly due to driveline vibrations caused by the lift:
-Shocks (The stock ones aren't long enough.)
- Transfer Case Lowering Kit (Cheap way, Not recommended.) or CV Driveshaft (Recommended This makes up for the added height which effects the angle on your driveshaft severely causing driveline vibrations.)
-Slip Yoke Eliminator Kit (cheaper) or Atlas II Transfer Case (not cheap) THIS IS FOR A TJ ONLY!!!! YJ's have Fixed yokes on the transfer case and so you don't have to worry. But, with a slip yoke like the TJ has, if you break your rear driveshaft on the trail, you're screwed b/c the shaft is just gonna fall out of the transfer case. By changing it to a fixed yoke, you give yourself the ability to pull the driveshaft out, throw it in 4x4 and drive out anyway.)
-Dropped Pitman Arm (For the steering gearbox. Some lift kits provide this.)
-Adjustable Track Bar (This is the bar that attaches your front axle to your frame. They make them for the rear too, but are usually only needed for the REALLY big lifts. Without this, your alignment will never be right.)
-Spare tire carrier (The stock one on the tailgate cannot handle anything bigger than a 31" tire for very long or your tailgate is gonna literally bounce till the hinges crack and break off.)
-Sway Bar Disconnects (Not required, but a cheap way to give you added travel in the front. Currie makes an awesome alternative, but it's not cheap.)
I feel like I'm forgetting something here..... But I think I've got all the requirements down.
YJ's are going to be cheaper obviously. The leaf spring suspension isn't going to give you nearly as much travel though if you end up in need of some serious articulation. A lot of people have started converting them to coil suspensions, but now you're talking more money. There are some additions you'll need, but I'll cover those with the TJ. Leaf springs are also easier to lift, but I never installed a suspension lift in a YJ, so I'm not going to tell you an estimate on hours when I haven't done it.
TJ's are a little more difficult to lift. There is a minor easy to fix issue with the 1997-2000 TJ's though. 1997-2000 had an issue with articulating in the front end too far and turning loose of one of the front coil springs. In 2001 they fixed the problem by installing a retainer clip. (I think it was the passenger side spring but don't hold me to that.) Easy fix, just get a retainer clip.
Recommended lift on a TJ to accomodate 35" tires is a 4" suspension lift with a 2" body lift. The 2" body lift helps alleviate the body slamming the tires. Technically, the wheel well of a YJ or TJ won't hold bigger than a 33" without grooving the tires when you really articulate the axle. That's why people usually combine the suspension/body lift to help alleviate that problem somewhat without trimming metal in the fender wells. Depending on where you live, you may also have to invest in wider fender flares if it's illegal for the tires to stick out farther than the stock flares.
And LAST BUT NOT LEAST!!!! WHEEL SPACING!!!! Many people don't realize that by going to a bigger and wider mud tire that the stock wheels often aren't gonna work for long. For one thing, you aren't supposed to go more than 2" over the width of the wheel. Most wheels are 8" wide, and most mud tires are 10.5"-12.5" wide. So, there lies problem # 1. Second problem is the wheel spacing on a stock wheel now with a wider tire has the wider tire sitting too close in and therefore creates a tire rub when you turn the wheel hard. Not good on tires.
One final note. Consider BFG Mud-Terrains. More championships have been won on those tires than any other mud tire on the market, and I personally can tell you I put nearly 40,000 on two different sets of them, and they were still going strong. I just traded vehicles both times.
Oh, and as far as timeline on a lift install. Depending on the level of expertise of you and your help, as well as whether you go with a basic kit or a long arm kit, it can range from a 1 day job, to a 4 day job. (Typically though, over a weekend and you're good to go.)
