I have a '13 JKU and currently running RK 2.5 max travel lift with the longer Rancho 9000s. I am thinking about upgrading it to 3.5. From my research, my options to do so include:

1. Cheaper Option - Upgrade kit to RK 3.5 Flex kit level. This would involve replacing the coils and the center link pins on the front sway bar links. Current lower control arms from RK 2.5 Max Travel kit will work.

2. Upgrade kit to RK 3.5 X Factor level. This would involve replacing coils and center link pin n front sway bar links. Purchase of upper controls arms Replace the rear lower control arm for longer units. Purchase rear track bar. Purchase rear coil correction wedges. Front lower control arms from RK 2.5 Max Travel kit will work.

Either way, I would still retain the rear track bar bracket, brake lines, front track bar, and bump stops from my current RK 2.5 Max Travel kit. Also, was informed that I could retain my current shocks.

From my understanding, I would need to replace my front driveshaft as some point. With option #1 I could go ahead purchase a new front drive shaft where as with the costs associated with option #2 I would have to wait a while to recover funds.

Would I need to replace my rear drive shaft or just whenever it needs it later down the line?

What are ya'lls thoughts on this? I currently run 35s and probably will for some time. Would you mess with this particular upgrade right now or would you put funds toward other things like air compressor, skids, upgrading front axle, etc.?

Side question...if I were to upgrade my front drive shaft now, take measurements and order new shaft (probably from Krawl Off-Road), would it be good to go if I later upgrade to 3.5 lift? Or will it be a little too short for optimum?

Thanks and sorry for all the questions. Just trying to line myself and funds out for my rig.

 

Personally I think that a 3.5" lift looks best on a JKU so I would definitely do the upgrade if I were you.

As for the driveshafts the front is the main issue. Since you have a JKU the rear DS is already fairly long so it will last for a while. With either upgrade you are able to adjust your rear pinion angle. Adjusting the pinion angle would prevent premature wear and increase the life of your DS. We have seen some of our customers go for 30k on the stock rear DS with the proper pinion angle.

I'm not familiar with the Krawl Off Road Driveshaft but I can tell you that Adam's Driveshaft's builds 7" of slip into the DS in which case will give you plenty of room for lift height changes.

PM us if you would like any pricing on the upgrades.

 

You have a 2.5" kit that fits your 35's, correct? Spend that money on other mods, then come back to this if you ever upgrade to 37's or larger.

If you do decide to go for the added height, go the cheaper route. No reason to replace the rear lower arms for the added length, just use the ones you have now.

 

Go with the 3.5" X factor. I have it and love it. Rides very smoothly and performs well. Make sure you have someone that knows how to install it. The rear can be weird and leave your coils bowed if not properly setup....it's no big deal...just make sure you get them as straight as possible.

I've driven my X factor for about 8-9 months now, wheeled several different terrains and have had no problem with my front driveshaft. I approach my rig as one big project at a time and understand what you're saying. Go X factor and do driveshaft later.


Edit: actually since you already have the 2.5", save your money and just get adjustable control arms all the way around. You net more than the 2.5" unless you are fully loaded (all steel armor, bumpers, gear).

 

I'm actually in almost the exact same boat as you. I'm running the 2.5" Max Travel and am considering bumping up to 3.5". I'm also running the longer Rancho 9000 shocks (part # ends in 31 and 32), I'm running Adams 1310 shafts front/rear, and I already have the coil spring wedges. I have a question myself about whether or not I'd have to change drive shafts if I bumped up another inch. I'll have to call Adams to confirm.

As for the control arms, I decided against going with the x-factor arms. Reason being is I read about folks having issues with rubbing of hard components (rear trackbar, coil springs, etc.) after moving the axle back an inch. I'm running 37's and ended up trimming both the front and rear pinch seam in the rear wheel wells. I also trimmed my stock fenders to flat fenders. I clear the 37's just fine with no rubbing whatsoever with my axle right where it is in the wheel well, so I see no need to move it back an inch. Should I go up to 3.5", I won't be anywhere near rubbing.

My plan will be to just buy the shorter rear upper arms so I can correct the pinion angle after raising it another inch, but that's it. Several manufacturers make the shorter rear uppers, to include RK by special request. I actually purchased TF rear uppers when upgrading to the 1310 shafts because I thought I'd have to adjust pinion angle in the rear, but it ended up being perfect without any adjustment needed to the rear lowers, so I returned the arms and left well enough alone.

I also considered both just adding 1" spacers, or a 1" body lift as cheaper temporary alternatives, but I think I've decided against that route. I'm not even 100% certain I want to bump it up another inch anymore. Since I'm not having any rubbing issues with the 37's (no added bump stop either), I think I like having the lower center of gravity and may just keep it as is. I also actually think the 37's look really good with the flat fenders and RK 2.5" lift, but I also think I got a little more than 2.5" out of the lift when I installed it. Maybe because of the lack of weight (shorty front bumper, synthetic winch line, rear bumper delete)? When I had 35's on there I thought they looked too small on the Jeep after cutting the fender flares. I'm afraid that if I bump up to 3.5" that it will make the tires look too small again.

I've yapped your ear off enough already, but wanted to give you my perspective. To answer some of your questions directly, I'd say skip adding to your lift right now if you haven't already done some of the other things you mentioned such as on board air, skids, beefing up front axle, etc. I'd definitely do ALL of that before adding anymore to your lift. And I'd run the stock driveshafts you have until you have to replace them. I wheeled for years with that 2.5" Max Travel lift on 35's, and I love the setup. I love it even more now that I'm on 37's. I replaced my drive shafts only because I landed on some rocks while wheeling and damaged both front/rear shafts. Spend your money on the other things for now. That's my vote.

 

I would choose other.
Yes your driveshaft would be fine and the driveshaft actually gets shorter not longer when you lift a short arm system unless you have a full set of arms and have the axles re-centered.