If you don't own a JKU on 40's with a 3.6 please don't tell me what you think of it.
If you can't remove your own personal bias because you want to do a motor swap but haven't please don't respond.
Really looking for the on road highway ability. 70's-80's possible constant? Or does it shift around a bunch?
I know there are many different factors but would keep it light weight as possible. I don't need it to beat my vette in a drag race. Just don't want to absolutely hate it. Really just trying to wrap my head around my next build.
I do not have a JKU on 40's and you stated you did not want an opinion, but I feel the 3.6 is a very capable motor I figure with proper gearing it would be more then able to move the jeep down the road on 40's with out issue. I base this on the fact I toyed with my 14 rubi with 4:10's and a flash paq 91 octane tune. It woke the thing up to the point my wife reilzed the thing had more grunt.
So even tho you did not want opinions from those not running the set up I do feel it could work very well with the proper gearing. Look at the little Toyota 22R and massive meat people have driven that little 4 banger around on. There is a hell of a lot more power under the hood of a JK.
I have a 2 door on 40's, does that count? I dont drive it on the highway or anything but I have absolutely no problems with the power on the trails. ~300hp with 5.38's turns 40s pretty well.
It may have just been my tuner, but I dont know if the JK's computer will accept a tire size over 37.
Well I have '14 with 33's, manual and it is a dog. Any incline forces multiple downshifts and sometimes barely hits the speed limit. I take it to the mountain for skiing/other outdoor activities and only to draw the conclusion that I need more power. I get passed by automatic jeeps all the time.
2015 JKUR with standard equipment (bumpers, winch, rocker protection, etc.) run with both hard and soft tops
I am on the highway a lot and in Texas you better be able to run 75 or better. With light weight 39 Krawlers on ATX locks with 4.88's it sucked bad enough I bought a BMW coupe last year. The thing was fine on flat or downhill runs but forget about passing or accelerating uphill.
I had OST Dyno make some trans tuning adjustments and it was a huge improvement but still not enough.
Off road things were fine with the OR tcase and I could generate the wheel speed needed for most situations using tap shift.
Sure I could have gone to 5.13 or 5.38 gears but then you fail to safely run 75 mph w/o spinning the 3.6 to 3000 rpm.
Couldn't stand the BMW so I shipped the JK out to Robbie and had him put in an LS3/6L80. Now 4.88 with Nitto 40's is no problem on or off road.
You should also talk about what your plans are on bumpers, skid plates, heavy duty axles, etc. and compare it to other people's experiences
This has a much bigger impact on performance than tire size. It just so happens that 40's often accompany heavy upgrades in all of the above to justify the tire size.
Going 35's to 40's with exactly countered gearing change will have some very very small number, perhaps 1-2%, on acceleration performance, and no real difference on an ability to maintain a constant speed up a hill (other than tire weight difference itself, which should be less than the weight of a passenger so not a huge deal there)
^this. @christensent speaks wisely ; rolling weight as we all know is something like 100 lbs of rolling resistance for each 10lbs of additional weight. It plays massively into the performance of any JK/JKU and whyi personally have the lightest ,while most strong,accessories like bumpers and armor and skids etc that I can run. The biggest hit in performance I still see is when my wife and kids get in the rig, heh. Loaded for bear - w full size spare and tools and recov gear and 10k winch my 4 door is maxed at under 4750lbs. It could weigh over 6000lbs - EASILY- so there is this con$sideration for aluminum where possible. I sacrifice the hardness of steel for the lightweight of aluminum whenever possible. the lighter you can get her ,the less hindered by larger circumference wheel/tire you'll be.
I gotta add that this thread is a great social commentary on / cultural reference for how our current society fails at basic communication : not at all effectively when you look at the hilarious number of direct replies that do exactly what OP asks them not to do in offering opinion with no f*ckng experience . It's amazing that we refuse to listen to even the most rudimentary request when in a public forum and behind keyboards like @Wannarun mentioned. :surprise:
I have a 2014 JKU with a ton of heavy things including 1 tons full under belly skid and a 40" spare. I am definitely not the lightest thing out there. I live in New Mexico which most places around here are above 5000ft. I also ski a ton in Colorado and drive the crap out of the jeep to go skiing. Just finished my last ski trip a week ago. LOL. It drives just fine with 5.38 gears and 40" tires. I can do 75 to 80 no problem. Temps run the same as when it was stock. The shitty transmission can be a pain sometimes with it not shifting up in gear but I just get off the gas and it will usually get it done. I am at like 2700rpm at 75. The jeep stays in eco when I have cruise on.
I drive my 2012 auto on 40s almost daily. I've put 9000 miles on it since going to tons and 40s this past August. I would like more power, but the 3.6 has no problems hanging at interstate speeds. And I'm running 5.13 gears.
I run 40's on a 2 door but I thought I would provide my opinion as I've been in some 4 doors on 40's. Coming from a 6.2, it will probably seem like total dog. If I did not put a sprintex twin screw SC on my 3.6, I don't think I could live with it and I have the 6 speed manual. Even still, I sit here thinking of when I can afford to put the LS3 in there. Automatic transmission would be a no way for me. Once you live with an LS, its hard to go away from it. I am interested in a turbo 3.6 because of the possibility to change the tuning to run higher levels of boost.
My $.02 - Find a similar rig and go drive it yourself.
For me, coming from a Jeep 4.0L and 35"-38" tires, it works well and I don't complain. My Jeep does not hunt around for gears on a mostly flat HWY at 75 , a small grade will put me in 4th, but no big deal. Steeper grades have gotten me into 3rd, especially when pulling 2 Sea-Doos. Going up to the mountains I use 2nd and 3rd with tap-shift, its fine for me, you don't need to go any faster anyways.
Once I get to the trail I forgot about it all anyways, and coming home is mostly down hill.
Loading up the Jeep with the family and camping gear I do notice the a decrease in acceleration and handling.
I would not say the Jeep is fun to drive on the road, the fun for me is off-road.
Fly out to San Diego you can borrow my Jeep for the weekend.
Side Topic - I should to be installing my 41.5" Pitbulls this weekend, I am hoping it doesn't change the driving characteristics too much. I am very happy with the current setup.
I have a 2 door But I do have heavy eBay special winch bumper with steel cabled Superwinch 9.5k, DV8 sliders & fender flares, and OR Fan rear bumper. My 2012 3.6L Auto has 4.88 gears pushing 37x14-17 Iroks (wheels and tires weight about 100-106lbs each).
I don't run any faster than 60-65mph normally. At times when off-road I feel 5.13s would have been better, but then it might be too much on the highway. I live in Florida where it's pretty flat. If I was living in central PA I know it wouldn't be happy going up and over the mountain.
People are just trying to help. Its not like people are coming in and just saying "yea you'll have no problem or NO WAY bad idea" without any experience. They are submitting good feedback on their known situations that can still be applied to OP's question.
I don't need opinions from people who haven't been there. There are people here who have gone down that path and I wanted their opinions. It's pretty easy to understand.
I would personally like to thank all the people who read this thread and said... you know... I don't have that setup. I'll keep my mouth shut. You're awesome.
2016 auto on UD60's/5:38's and 40's. VKS bumpers and sliders. No spare and ARTEC aluminum skids. I like this better than my 2011 auto with a RIPP on 37's with 5:38's. Shift points are a lot smoother on the 2016. Gets out of it's own way and can pass on a 2 lane no prob.
I've had 3.8 on 40's ls3 on 40's and Lt1 on 40's all in 4 door JKUs. And have driven multiple 3.6 JKUs on 40's. My thoughts on it are
3.8 and 40's is pure shit
the 3.6 on 40's will be fine for most people. It has decent power but needs RPM to make it.
Ls3 is smooth and how a jeep should drive
Lt1 is a torque monster and the way I prefer my JKUs.
Andy, the wife may be content with a jk on 40's and a 3.6. But coming from your bad ass TJ it will make you jaded. And you seem to like to mod your toys, so slap the tons under the JK until you can't take the 3.6 any more. Then drop an LS3 or LT1 in and have best of both worlds.
It's only money, they give it away free at work and you can't take it with you when the reaper comes calling .
I am, however, struck with how different people's perception of adequate power is.
Same vehicle can be "plenty of power to pass" to one guy, and "dog slow" to another.
My experience says that the Jeep owner is a restless soul and the mod process is never done. Slap them big tires on that you know you want and sort out any power issues that may arise later.
This is the reason for my inquiry. I kinda feel like people are 50/50. Everyone processes their answers through their own filters so you never know if someone will justify their "enough power" statement through the filter of.... I can't afford it so it is just fine. It is also different to understand "enough power" for those that have never driven bigger power.
At the beginning of planning stage it is very important to be honest with what you want and shoot for it. So a motor swap to me means different axles versus the axles I'd use with no motor swap. I will stay up late and figure out $$ for both avenues and then obsess over it until I pull the trigger.
I've had a 7 year build on my TJ. I don't want to get into that again. But I can't stop my marble from spinning on the next build.
I am, however, struck with how different people's perception of adequate power is.
Same vehicle can be "plenty of power to pass" to one guy, and "dog slow" to another.
My experience says that the Jeep owner is a restless soul and the mod process is never done. Slap them big tires on that you know you want and sort out any power issues that may arise later.
It's a slow day and internet time is cheap, so forgive th sidebar.
I am swapping a front axle now to fix the "JK smile" that has somehow occurred on our little rig. Tell me about your axle thoughts regarding 40s with stocks power vs. an LS swap.
Please also see my sig, and note that I completely understand your statement about the problem of going from V8 to a smaller motor.
Provisionally:
Stock motor = Ultimate Dana 60's.
LS3 = Dynatrac Dana 80's.
Of course... I'm still in the thinking phase.
I currently run a 6.2 with Torq14's front and rear on 43's. I like to over build so my rig stays together when I go play. I'd rather have more Jeep than driver.
2016 JKU Sport S running 3.21s with 2.5" lift kit and 35s. It felt a bit sluggish at first, but I don't even notice it now. There are so many other things I would rather spend the money on than regearing right now (like the Poison Spyder Ricochet Rockers I just purchased that are getting installed on Tuesday).
I beat the piss out of the Ud60's with the LT1 (L86) and they are solid. I ran 40" sticky trepadors all week in Moab, been to Colorado, fordyce, JV etc. mashing the throttle for giggles. I did gusset the TB brackets beforehand as they are a known weak spot. But I have yet to hear of a broken axle shaft from hard wheeling. Unless you jump the pig amd snap the housing in half.....:grin2:
I have a 2016 JKU-R with stock 3.73 gears and 37" tires. Honestly, it doesn't do too bad on road. I also have the SuperChips F5 tuner, and that wakes the engine up a bit, too. Offroad in low range it crawls like a beast.
So if you were to go with 40s and gear it accordingly, I think it would do pretty well.
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