Upgrading Rubicon Express 3.5" Kit To 4.5"

I currently have a Rubicon Express 3.5" super-flex lift kit installed on my '96 XJ, and am considering upgrading it to 4.5" specs. From my reasearch it appears that the following parts are the only differences between the two kits:

RE1141 -- swaybar disconnects
RE1310 -- 4.5" coil springs
RE1550 -- front brake line extensions
RE2700 -- rear leaf spring shackles
RE3781 -- upper control arms

I notice that the 4.5" kit uses leaf springs from the 3.5" kit and gets the extra 1" rear lift from shackles. I currently have .75" coil spring spacers to level the XJ out.

1. Could I just use my 3.5" coil springs with thicker 1.75" spacers (1" thicker than what I have now) instead of purchasing the 4.5" coil springs?

2. Will my current Old Man Emu shocks that came with my kit still work with 1" more lift?

3. Will I have to change my rear axle shims?

1 Yes.

2 Probably.

3 Maybe.

Robert

WrenchMonkey said:

1 Yes.

2 Probably.

3 Maybe.

Robert

Click to expand...

X2

spring rate will be different, so shorter coils will have less travel and be softer, bad mix for off-camber at height

1. Yes
2. Probably, mine were fine.
3. Doubtful (but maybe). I have used the same 4* shim from the RE3.5 kit up to a 6" lift.

ehall said:

spring rate will be different, so shorter coils will have less travel and be softer, bad mix for off-camber at height

Click to expand...

I can't imagine there will be that much difference.

Care to educate me?

Robert

I upgraded my RE 3.5" kit to a 4.5. First I had 1.75" spacers in there to level it out because my leaf packs are extremely stiff and ride a lot higher than the front springs do.
Anyway, I put some Skyjacker greaseable shackles in the back to get it to be "4.5 inches" (actually it's more like 5.5 for me), and went with a 4.5" RE coil. The 4.5" RE coil is softer than the 3.5" was. Also, you'll need to get some bigger sway bar disconnects or make the ones you got with your kit longer.
As you stated, you'll need longer front brake lines, but I just kept mine the way they are for now without any problem. I still haven't upgraded my upper control arms, maybe I will sometime but I'm holding out for some drop brackets and I'll probably go with uppers and lowers then.