I have a 2004 Rubicon.  Right now it is bone stock.  I am looking to put on 33" tires and was wondering how much lift I will need to clear the tires.  I was thinking of maybe 3.5" Rubicon Express Lift.  Are there any other mods needed w/ a 3.5" lift?  

Didn't Rubicon's come with something close to a 33 stock?

3.5" should be plenty to clear the 33's. With only 3.5" of lift you shouldn't have to do anything else. Any more and you would be in the SYE area. But even then that and a new driveshaft would be the only mods.  

It's a Rubicon...he won't need a SYE. There's no slip-yoke to eliminate.  

If I was in your shoes (which I was)  I would go for the Rubicon Express 4.5SF with the 3.5 Springs.  That kit is more complete I also upgraded to adj. uppers to help pinion angle.  With 3.5 coils and a 1'BL you can clear 35's.  

Don't believe the hype!  I have an 02' TJ that I have been running 305/70/R16's (33") MT/R's on for several years with the 2" OME kit with heavy springs.  I just installed a 1" body lift and plan to run 35's when the 33's wear out.  If your bumpstops are lenghtned appropriatley you shouldn't have any rubbing, which would be at your fender/fenderflare connection.  Bumpstop extensions should come with the lift kit.  A buddy put a RE 3.5" short arm kit on and he could clear 35's with ease.  I believe that the kit comes complete but you should do a CV drive shaft conversion too.  If the kit doesn't come with adj. u.c.a., you will need adj. upper control arms to adjust the pinion angle on the rear diff.  I just did this to my Jeep because I added a Teraflex Belly up increasing the angle of rear driveshaft.  Rotating your rear diff. twists your axle tube thus changing the angle of the rear spring perches.  So, the springs don't sit perfectly.  I am looking into buying a bracket from Nth that corrects this problem but it lifts the rear 1.5".  

Do wan't your Rubi really tall? I run 2.5" OME in the rear and 4" (3.5) ProComps up front with 37's on my LJ. Keep in mind my wheel openings are not stock but I can run 40's no problem.(well problem... I need bigger axle's)  
 

What ever lift you go with it is best to have adjustable control arms, make sure you get a dropped pitman arm so you can keep the track bar and drag link parallel to each other or you will get bump steer. A good kit will get you everything you need. I have a 4" lift with 35" tires on it but I also had to build up the bump stops that came with the kit to keep the tires out of the fenders. With 33" tires you shouldn't have that problem.  

Cut your fenders  

Hey Sean how do you like the TNT lift on your jeep?  

the reason for the standard of 4 inches for 33's is for maximun travel and articulation, sure you can fit 33's under a 2" but when you get done putting long enough bump stops to keep the front tires out of the fenders, there is not enough up travel left to soak up a speed bump at the grocery store. try driving with the sway bar disconnected when the axle is using a bump stop for a pivot point.  

i have a 04 rubi also. i started with a 3 in day star and cleared 33's but it rubbed only in sharp right turns.  i then went with a 6in rough country.  no problems at all clearing 33's.  when they wear down i am going taller tires.  they make a 4 in lift that will clear 33's easily also, and for the money it is worth it.  if you want to go taller later all you need is the springs.  rough country lifts come with your drop pitman arm, control arms, springs, shocks, rear location bracket for track bar and either a relocation bracket or adjustable track bar for the front. they also have many extras if you want.  as for the sye and cv shaft forget them, you DO NOT NEED THEM.  

you will wish you had that SYE and CV drive shaft because of the vibration problem, unless of course you are sporting a set of swampers, wear ear protection, kidney belt, and a mouth piece to keep your teeth from chattering.