Jeep JKU; 35's vs 37's and drivability

[Greg]

Looking for opinions on how 'road-trip' friendly a JKU with a 3" lift and 35's would be compared to a 4" lift and 37's. I'm not worried about offroad capability, but how well a JKU will travel on the freeway for several hours on end, how well it would ride, drive, etc. Most of my trips will be more mild 4x4 trails, camping along the way, etc and I want something that doesn't wear me out after long or even several days on the road.

For a little more info, I'm considering picking up an older JKU and (eventually) swapping in a GM 5.3l V8 with a 6L80e 6 speed automatic... so lacking power won't be an issue, which can be tiring on long trips. I think a 5.3 will turn 35's with little problem but 37's will knock down the MPG's and power somewhat. I realize most guys don't have V8's in their JKU's, but I'm more concerned about how well it would ride & drive. I'm leaning towards a 3" lift and 35's.... but 37's sure are tempting. Keeping it lower and on smaller tires seem smarter for my needs. Any thoughts?

 

[N8RB8R]

My JKUR was ok to make long distance trips when it was on 35's with 5:13's. As soon as I upgraded to the Tera axles with 5:38's and 37's it was very uncomfortable to try and drive it any distance at freeway speeds, I had large upgraded Trans coolers as that was a must and it was wrapped out due to overdrive being useless.

The AEV procal made a huge improvement in the drive ability and in my opinion would be a must do upgrade.

Then I finally realized I hated trying to drive it anywhere at that point and a v8 was a must, so it ended up on full width tons with 40's and traveled everywhere on a trailer.

Looking back I wish I would have just kept it on 35's and enjoyed it. They are a very capable rig with few mods to take you just about anywhere. I would hold off on 37's until there was some real power under the hood.

 

[Greg]

Great info Nate, thanks for taking the time to weigh in! Makes me feel like keeping it on 35's even with a V8 would be wise if I want to drive it long distances. I'd probably leave it close to stock until I got the V8 in, then work on adding the lift and bigger tires as the 2nd step. I really don't want to gear the stock axles deep for the V6, so better work on a bigger engine first, then worry about gearing later.

 

[mbryson]

I think it depends on which axles you're running. Stock JK axles (even the bad ass Rubicon D44) aren't overly friendly to 35" tires. I think you open up your options with the V8 quite a bit. I've read of guys adapting SuperDuty axles (I guess the tone rings work with the stock JK computer?) to their JKs. A set of 4.30 axles, 37" tires and a 5.3L/6L80 would be quite a combo IMHO. Probably quite streetable as well?

FWIW, we drive my 35", 4.88 geared JKU to the tune of about 15-18k per year so far. I think we need a Maxima or Accord or something but that's a whole different subject. With the 3.6L, I'd have rather went with 4.56 gears vs. the 4.88 but it's not bad enough I'd spend to change gear ratios. Just an FYI on my rig (updating my JKU build thread one of these days), the tallish winch I have restricts airflow enough on hot days and long freeway climbs to cause a pretty significant temperature increase (say driving north out of St George or similar---I can make Parleys but it's close). Enough that the engine computer starts limiting your available throttle and you can't maintain speed (big brother car). I just bought a different bumper to recess the winch down to not block airflow.

Even with the 35" tires, 3" Tera lift, you notice wind gusts and such. Taller wouldn't be better, IMHO

Oh: and maybe to add to your question. I've not been overly impressed with my hardtop. Does someone have dual tops and could speak to quiet of the "improved" soft tops vs. the hard top? Aside from the minor security differences, I'd just as soon have a soft top vs a hard top. Anyone else?

 

[Greg]

Regarding axles, I'm under the same impression you are... stock axles just aren't up to par for bigger tires, even 'small' 35's. If I could keep the stock rear and run an aftermarket front housing, I would... but with a V8 I'm not sure that is the best plan.

I'll probably reinforce the stock front axle for the time being, but not plan on spending money on gears or lockers in the stock axles. I've been considering Teraflex axles, possibly a Tera CRD 60 rear and a Tera 44 front, but that would probably happen later in the build, after the V8 swap and suspension changes. Gear ratio is one subject I'm not sure about... I want to gear for efficiency and road driving. With the GM V8 and 6 speed transmission, I can gear it deep and still keep the RPM's down low on the freeway. The 6L80e has the following gear ratios;

1st- 4.027
2nd-2.364
3rd- 1.532
4th- 1.152
5th- 0.852
6th -0.667

I could run 4.56's and 35's and be turning 2,200 RPM @ 75 MPH. I think that would allow for great driveability, keep the RPM's down and still get decent mileage.

I think you're right on the 35's, 3" lift and wind gusts... lower is gooder.

 

[Hickey]

I have dual tops. There is more noise with the soft top, but it is far less than the old CJ soft tops I've had in the past. Hot/cold insulation is not really noticed. I freakin love my soft top, but I think I would rather have the Trek top. The trek top leaves you with a sweet safari top after you zip out the windows. The factory soft top still has the rear "legs" that look a bit lame once you zip out the windows.

Having recently purchased a spiderweb shade, I now consider them a mandatory accessory for every wrangler, especially if the occupants are middle-aged bald dudes.

For your lift, consider only buying 1 3" lift. You can easily fit 37" tires on a good 3 lift.

 

[Hickey]

Ruff stuff has a diy long arm kit. I'm seriously looking into getting this, even though I only have a 1.5" lift.

 

[moab_cj5]

I have a 2010 JKU Rubicon. I bought it with the lift, tires, and gears already installed, so I have no stock basis, but I don't find mine to be obnoxious on long road trips. It is gutless even with 5.38's turning 37's, but it is manageable. I don't love my lift, and would probably go with teraflex or metal cloak if I were to start from scratch.
I have replaced my front axle shafts, and had the front sleeved and gusseted, but I don't worry much about my front axle because I am not heavy footed off road.
The best advice I could give, is take a few different setups on some rides and see what you like. You are welcome to take mine for a spin if you are ever over this way.
I personally like the 37's because of how long the Jeep is. For the wheeling I like to do, it isn't always an issue, but I like having the extra clearance.