Even though the KM3's tires are more like a true 37" you are going to want assist. don't forget the extra width. Stop the denial and just plan for it.
No denial, Tom. Just dragging my feet and being stubborn. I was doing just fine with a the stock steering gear with 37" Nittos and aired down to 7psi. My box was ported and I had all of the new hoses and ram and metal tabs to finish the job on my D44 but never installed it. Sat on the shelf for a long time.
I wasn't originally plannign for tons or tires larger than 37 and just put the PSC big bore in so I'm going to run it a while before replacing it with the ported version and a ram. I got the non ported version. PSC say its great up to 37s. I ran Nitto 37s, which recently sold. Those are not true 37s. they barely measured 36" when new IIRC. I don't feel (at least not yet) that I'll be pushing the limits that much with the big bore and the KM3s.
My stubborn ass will drive it sans-assist for now. If/when I go to assist, someone is getting a deal on a used big bore. I won't sweat it.
What will you be doing with this Jeep? If your going to wheel it you will want hydro not that super expensive gimmick of a box. Is it because it’s says 39s on the sidewalls and not 40? You’re dropping some nice coin on some quality axles I would at least make sure the steering is set up proper. I only run 37s and I don’t know why I waited a year to install my assist. Best mod I ever did and it’s been problem free for five years and no I’m not running a fancy psc system. Thanks to this great forum I installed my system for less than $700. Do it once do it right
I'm not too worried but will play it by ear. I've been doing fine with a stock box and 37s. I've wheeled the Rubicon and other, similar NorCal territory.
I had a steering ram and hoses sitting on the shelf. I also had a synergy sector shaft brace and pulled that off after brief use. You could say I was freeballing it on 37s up until now.
I'm completely happy on 37s and as far as i know have done all but the hardest stuff on the Rubicon. No soup bowl and I've only done 2 of the 3 Sluices. Sorry, I still confuse the names.
Only reason I am feeling compelled to go larger than 37 is to compensate for the small amount of clearance lost with the wontons. Discussed this in other threads.
I know someone running 40" Nittos on a stock steering box without a ram. But it's a two door and he really knows how to wheel. Won't mention names.
Edit: I also have the PSC pump and high flow hoses and reservoir already. Hydro assist won't be difficult to add.