PSC makes a big bore box they say is good up to 35" without the installation of cylinder assist. That's our end goal on the '18 2 door that runs a small 37 (35 3/4") . LINK
But if you're going bigger, and if your Jeep sees a lot of trail time then the cylinder assist is the way to go. Expensive yes, but worth it in the end.

You know the drill, 37s+ need a lot of mods, especially if it's a trail Jeep. There is no easy or budget friendly way to get there. Or at least the "budget friendly" ways are still expensive in my book. So whatever you do build towards your end goal. If you already have the axles you want then go ahead and buy the best steering kit you can justify. If you don't already have the axles you want then plan accordingly. Build with the end in mind.

Here's the PSC cylinder assist kit for a stock JK
SK281 - BIG BORE XD Cylinder Assist Steering Kit for 2012-18 Jeep JK 3.6L with OEM Axle

 

The full blown Psc big bore kit can be found for around $2200 on sale. With 37s you could possibly be ok with just the big bore box but that would also be hard on draglink and frame.
Red neck ram can be a lot cheaper as long as your box is in good condition. RN ram will be a little slow turning in parking spaces from what i have heard. Some have fixed that with an upgraded pump.
Howe does a great job rebuilding your box and adding internal stops. No idea on price but I heard they are expensive.
I have no idea about AGR system but Genright seems to use them.

 

The PSC xd2 box is good for 37's...that 2k setup is worth every penny...I talked to the PSC rep for 3 years at Jeep invasion before I bought mine...as for the track bar just get a synergy track bar brace...I have a whole season on it now and it is leaps and bounds above the stock setup...over 37's is when PSC recommended hydro...it's one of those mods you go back and forth on but once you bite the bullet and install it you'll be super happy with it....

 

another vote for PSC. Its a buy once cry once for me. I have the box right now + the synergy brace but plan to drill and tap when the time comes to do so. Sometimes you can catch a stellar deal on the whole setup (normally around black Friday).

 

I am in the middle of installing the PSC Big Bore steering box. I also have the hydro assist kit as part of the deal. I hope it is everything I think it will be. Box and pump are installed, but I am still running the lines. I do wish the kit had better install instructions, but I am figuring it out so far. It is like doing a jig-saw puzzle without a picture of what it is a picture of.
One of my issues / questions is I am currently running a flipped draglink. But their bracket to attach the cylinder to the axle is made for a non-raised track bar. And so far I have not found a cylinder bracket for a raised track bar. I can go back to a standard track bar and un-flip the draglink. Or I can try to figure out how to keep the raised track bar and flipped draglink.
As to your current issues, it sounds like the install job wasn't done quite right. There are two aspects to centering the steering, adjusting the drag link to the correct length is the more common aspect, but there could also be an issue with how the pitman arm is installed on the steering box output shaft splines. The PSC Big Bore box has splines that only allow one of four possible installations of the pitman arm. I am not sure off hand how the stock box is. But it could be that the pitman arm is not installed with the correct orientation, that coupled with the incorrect length of the draglink might be why it is the way it is.
That said, I would not hesitate to go with the PSC hydro-assist kit (well, clearly I already did). For bigger tires (we have 37's) it can be impossible to turn those big tires in some situations. With the hydro-assist I hear it is no longer a problem. You only need to worry about not damaging your wheels and tires. Something will have to give.

 

Alrighty....have some more new info for the big box or ram equation....this weekend I was at Rausch creek wheeling and it just so happens there was an event there and PSC had their ginormous trailer there...well being that I love their stuff I meandered over there and was just gonna buy a shirt...started talking to the guy and now the xd2 big bore box is good to 35's....well you guessed it I was like "wtf?" You just told me it was good for 37's not 1 year ago...well in January they got a new CEO and he started looking at all the failures and warranty work....turns out the xd2 box is strong enough to work 37's and the sector shaft is no longer the problem...now the problem is the bolts that hold the box to the frame....after a while anyone running 37's is sheering the bolts right off....so now they recommend hydro assist for 37's....so I walk over there to buy a t shirt and walk away with a t shirt and 400 dollars worth of ram assist parts and fluid .... fortunately I ordered the xd2 with ports for that just in case moment so install should be pretty easy....

Figured I'd follow up since I was spouting the other message they gave me last year......

 

I have a PSC hydro assist and love it with 37s. I have known a few people with the “big bore” box and have heard mixed results. A fair number of problems.

it sounds to me like your new box maybe wasn’t installed correctly. Unless you’re just dying to spend money on an upgrade, I would investigate whether you can just fix your current problem by ensuring correct installation.

 

What problems?

 

I have the PSC big bore box+pump. I just moved up to 37s and it moves those tires fine. I do get a little groaning from the pump, but I had to reuse the stock reservior instead of the big PSC one due to clearance issues. I will probably add the trackbar brace to the near future upgrade list.

 

If you are going to 37's just do it right and get the PSC hydro assist kit. One of the best mods we have made.

 

I also need to upgrade my steering but I'm always wondering why the Big Bore XD box is needed with the hydraulic assist ram? I understand a stock box is the weak point, but if the ram is doing the work, why is a heavy duty box needed? I understand that it is important to have a new pump with higher pressure and flow rate along with a better reservoir and cooler, but what's the point in the big box? Howe rebuilds stock box and installs steering stops. AGR uses a Chevy? box with internal stops, RNR uses a stock box. I want to do it right but I'm not sure the most popular kit is also the best? I get that if the ram fails or has a leak you can cap off the lines and run the box; but, that is a lot of money to have a stronger box in case of failure. You can cap off any of the other boxes and still wheel with more effort. If the pump fails the whole system is down and any box may be damaged by debris. Before the JK so many successful ram assist steering systems were built off stock boxes with great success.

I sometime feel the JK market has changed some products for the worse.

Another question, would this be a better but harder to fabricate way to mount the ram? Wouldn't this help reduce misalignment with the tie rods?

 

You don’t need the big bore box to run a ram. The big bore started as a substitute for a ram system. In my view, a poor substitute because it puts all the extra stress on the drag link rather than dividing the forces between the drag link and the tie rod, as with a ram system. People then created demand for a ported big bore box, to run it with a ram. True, the big bore does get you a stronger sector shaft. That can provide some peace of mind; occasionally sector shafts break, and if they do, you’re pretty much stranded. A cheaper alternative is a sector shaft brace. I’ve run a synergy brace for years. Haven’t broken a sector shaft yet. Perhaps if you are running 40s or larger, the big bore plus ram makes sense. Otherwise, the regular PSC box with a ram does just fine. No matter what, if you are rock crawling, I would add a cooler.

 

So bottom line, there really is no need for the XD box?

 

If you go bigger than 35's than no...if you stop at 35's then it's a solid upgrade...hell...it's still turning my 37's...

 

It's not the socket head that's the advantage. You are comparing grade 12.9 to 10.9

 

I'm curious what bolts go where with that kit? I have the psc big bore box and it came with 2 10.9 bolts to use in the front 2 holes. The rear holes reuse the stock bolts. I imagine you would want some additional length on the bolts if they are going through the synergy bracket now. Do the 2 new bolts replace the 2 stock that are left? Or do these go in the front and the old 10.9 move to the back?

 

As I understand it, with the PSC Big Bore steering box the key bolts are the two front bolts that hold the steering box to the chassis. The rear two bolts can go all the way through, if the bolts are a little too long they just stick farther out the other side. But the two front bolt holes don’t go all the way through. So if those bolts are too long and you tighten them anyway you will bust the steering box casting.
The kit comes with two bolts that are the right length for the steering box without any additional brackets or spacers. If you have a bracket that sits between the steering box and the chassis you need bolts that are slightly longer than what comes in the kit. If you use the shorter bolts with a bracket you won’t have enough threads engaged to achieve proper torque.
I torqued those bolts and applied blue loctite. I used 87 ft/lbs from the chart BBS posted in my thread on the PSC kit.

 

Glad I checked the torque on mine today, one was completely loose. Torqued to 80ft•lbs. These are 10.9 M12x1.75 which spec says 87ft•lbs, but I’ve also seen people say 70, so I sorta went halfway in between.