Track bar relocation brackets, springs, shocks, controls arms, bump stops, brake lines, front and rear driveshafts, potentially an aftermarket front axle to maintain caster and decent driveshaft angles.
Why do you want more lift? It gets very expensive on a jk to maintain decent ride and handling with any kind of durability or reliability.
do it right about 1k per inch at 3" and up. Stay under 3" and it is less. Jks do very well with 3-4.5 ish on short arms(stock Jks are not that short of arms). 4.5 to the moon is longer arms.. give or take
The springs WILL come out if set up like that and I have SEEN it happen. More common on Tjs.
I bet you have spacer lift that has sagged springs. stock springs are constant rate and cheep as he!!.
So you recommend new springs?
And would springs be all that I need to lift to 4 inches?
Would that be softer then the spacers and stock springs?
From those pics it looks like they are still the stock springs. And tires look to be about 33's which you mean you might have a 1" lift. Also those are shocks are completely wrong you are overcompressing them. They should have more rod showing when sitting at ride height than that.
You need to do a lot of research into what you have going on down there. More pics of the spring perch, pics of the numbers on the springs pics of the steering as well as a pic of the lower control arms will help us out a lot.
It's obvious you don't know much about cars (Jeeps) -yet. That's ok, we were all young once.
Let's figure out what the issue is (are) before you start changing things for the sake of change.
Other than the 'certified firestone tech' what issues are YOU having with your jeep, and what do you want from it?
Are you wanting more lift, or bigger tires? Are you having problems with clearance as is?
The difference in perceived ride between you and your buddies Jeep could be as little as stock spring rate or even tire brand or or pressure.
Haha yeah I'm not very knowledgable with lifts at all.
My ride is really hard, even with my tires at or around >20 psi.
When I go offroad and hit small bumps or even just speed bumps in a parking lot the suspension is stuff and sends me flying above 5mph. I want a softer ride :P
I've seriously never driven a car with such hard suspension.
I have bottomed out the diff once already but clearance is fine.
I like my 33's.
so, what you have is easily fixed. There are a great amount of very good vendors that can help you. Like others have said, first, figure out what you want, how high you want your lift to be and what you are going to use it fore.
AEV, Rock Krawler, Tereflex, MetalCloak (possibly more expensive) just to name a few all have great 2.5" lifts and lift kits that you can get that provide excellent ride and road manners as well as the ability to go off road with a nice degree of safety and a lot of fun. With any lift, there are pro's and con's. How do you plan on using your Jeep? daily driver? A lot of road miles with little to no off road? Off road? What type? Easy trails, rock crawling, sand, mud? All of that helps with decisions? Also - Chat with a vendor or here such as Jason at krawl Off Road or someone at Northridge 4x4, etc.. and they can help steer you in the right direction and give you a lot to think about.