mtngoat64

Anyone have any issues running a lifted JKU on 35s with a 3.21 rear? Before I move forward I'm trying to figure out if I need to upgrade to a 3.73. Would prefer not to since most of my driving is on the hwy. Thanks.

LordV8R

I will be doing the same thing. I was going to try to wait in tires until I had money to rehear, but I'm not that patient, lol. I have a '14 with the manual, I can't imagine it to be to bad, maybe like towing a small trailer. 4lo will be really fast on the trail though.

Sent from somewhere I really shouldn't be!

Dahmer

I have a 11 with 35s, yes I know it's a diff motor and trans. I had 3.73 gears originally and it never shifted into over drive it had no power and was the most awful driving experience. I got 4.88 and it's not very far from stock. I can imagine with that gear setup you will experience similar problems. Also I forgot to mention that the upgrade has paid for itself in gas mileage returning to stock, 11 mpg was killing me.

jadmt

I had a 13 jku with 3.21's and 32's (285/75-16) and no way would I have been happy with 35's. it will be a slow pig and your crawl speed will require riding the brakes all the time. It was fine around town but on the highway it gets into the never in the right gear playing game. I have a new 14 with 4.10's and I think that is border line for true 35's. I

Invest2m4

35s on 3.73s borderline sucks. I have a 2013, light 2 door and 35 (closer to 34") Duratracs, 6 speed manual. I'd call it tolerable on flat roads. Highway was pretty much always 5th gear, rarely 6th. LOTS of downshifting on the highway. I've since moved to 4.88s (going 37s).

In reference to the 4-low comment, that was even worse! My Jeep was 3 months old when I swapped in a 4:1 rubicon transfer case. I wouldn't recommend 3.21 even with stock tires.

And note that 3.21 does not mean better MPGs. My Jeep with 3.73 and 35s got worse mileage than my buddies same setup, but he had 4.10 gearing. Why? He could cruise in 6th gear on the highway and spent less time downshifting to higher RPM's.

I can't imagine a JKU with 35s and 3.21. Doubt I'd ever leave 4th gear... 4.56 is probably ideal for 35s. Have to say that 4.88 is awesome though.

kh202

Man 3.21's and 35's really isn't all that bad. Forget 6th gear, but 5th puts you in perfect RPM range and I rarely had to use 4th above 55. Sure your experience maybe different if you live in mountains. Offroad isn't terrible except for the rocks. You'll stall a lot lol. I swapped in a 4:1 case and it was just fine tho.

People all have different opinions on what performance should be, it's all relative. Friend of mine dd'd his '10 with 3.21s and heavy ass 37" PB Rockers. I even towed an 18.5' boat that was 2000+ lbs.

ibanez0154

I don't have a jku but I have '13 w/3.21's and only have tubi take offs. Same as you said, I would not even think about 35's with this setup.

mtngoat64

Thanks everyone for your input. It will help me decide to go smaller on the tire or upgrade my rear axle. Currently, my JKU with manual transmission works perfectly with stock tires, trying to gauge the impact as I swap components. Thanks again.

crodgers618

X2. I have a 07 and have been running 3.21's for a year now with a superchips is not a dog and does ok off road. Mpg isn't that bad either. I've been told auto is bad.

clemsonkrawler

I have a '12 with 3.21s, auto and 35 MTR/Ks. I live in Colorado so I spend a lot of time in the mountains. Its definetly liveable. I put the lift/tires on last summer and have had it out wheeling quite a few times. It does hunt for a gear on the hills driving down the highway at 75mph. Im going to regear to 4.56s this week.