Jfk70

When I first got my jeep and was considering a lift and bigger tires I was worried that without a gear change and upgraded drive shafts I would be left with a vehicle that was either so slow that it would be embarrassing to drive because of the factory 3:21 or would leave me sitting on the side of the road because of a broken driveshaft. So I wanted to share my experience. I have had a 3.5 lift and 35 inch tires installed on my 2016 JKU with and automatic trans and 3:21 gears for 3000 miles. I haven't noticed enough of a difference in acceleration around town to concern me about a gear change however on the highway I have noticed that it puts a strain on the vehicle to drive 80 miles and hour and that is about my top speed. So in the future they will be getting changed. -"As for the drive shaft I haven't had any problems as of yet and I haven't noticed any tears in the boot. But I must say I haven't done any extensive off-roading with the exception of a few brief trail rides.
Hopefully my luck holds out.

Canvas

Congrats on the new Jeep and welcome to the world of what to do next. With that being said I have a couple of questions for you.

What is you final tire size you want to go with? Reason is you only want to regear once as it is quite spendy ranging from $1500-2100 depending on where you go. Below is a standard gear chart that will help you decide.

What type of wheeling do you plan on doing? Again the type of wheeling with the tire size will determine what gears you want to go with.

As for your driveshaft I would run it as long as you can until it fails then replace with an aftermarket one only and if only you upgrade to a D44 or higher. Reason being that when you regear you want to keep your weakest link anything other than your Ring and Pinion. I ran 5.13 gears with an Aussie Locker in my D30 and wheeled in Moab with only one slight issue. I kept the stock axle shafts and drive shaft so that they were my weakest link. It paid off during EJS 2016 when I was on Rose Garden Hill where both front axle shafts ujoints failed. Had I put Chromoly axle shafts there would be a regear during the trip.

For me I know that 37's for my current set up will be the biggest I will go my choice was 5.13's.



R/
Will

Jfk70

Thanks for the Reply. I plan on upgrading everything that is currently in place EVENTUALLY. When these tires need to be replaced I will move up to 37 followed by 40s ultimately. This should put me on the 100000 odometer range when the 40s are installed.
I will also lift it more as I go. My first thought is to go to 4:56 or 4:88 gears, not quiet sure yet. But I only want to do it once. I have a local shop that will do a complete gear swap with Yukon gears and even boost my carrier size for 1,200 range. Parts and labor.
Most of what I plan on doing is 80-90 percent highway and light trails, and some swamp mud. Been holding off on the swamp mid till I am done phase one. Want the new drive shaft in place (woods or Adams I figure) and the gear change before I bury it in the mud.
For the most part I don't expect to be doing much, if any rock crawling.

nthinuf

Since 37's/40's are in your future, have you started thinking about axle upgrades also? Might make more sense to not regear the d30, and just wait until you move up to something more appropriate to 40 inch tires. And if new axles are in your future, you could end up needing different driveshaft lengths.

Just a heads-up to lay out all of your upgrade plans so you aren't spending money two or three times on the same things.

Jonathan_JK

At least you know the Jeep disease. I said "33's is as Big as I want to go" now I'm at 37's and looking at 40's. But If 40's are you goal I would Suggest 4.88. I put in 4.56's and now I wish I had done 4.88. I'm going to be putting in a ProRock 44 in the front soon so I'll just have to re-gear the rear. I would not waste any money on the D30 If you do Rock crawling.

Jfk70

Yeah I probably will end up with the 4:88 on the first swap. Haven't thought of new axels yet because I am hoping for 50k miles out of this set of Kelly 35 tires. But I may be a little optimistic since they are AT tires that will spend most of their life on hot Florida roads. However I have gotten longer life out of Kelly tires than other brands. The axels will be a consideration on tire set Three but I don't think that will be for 5 or 6 years.
The vehicle came stock with 30 front 44 rear with Trac Loc diff. And I don't plan on Rock Krawling till the jeep is old enough to be an off road only vehicle.
Besides the gear change I also want to get adjustable control arms on the lift instead of the ones that came with the rough country 3.5. Could use a little camber adjustment. Still a little flighty at 80 miles an hour. Maybe I'm just getting use to the lift vs factor height on pizza cutters.
I could def tell a difference when the drop pitman arm was added. Without it driving the highway was quite sporting to say the least. rough country forgot to include it in my first shipment so The had to send it a few days later.

metaldemon

I have a 2012 JK 2dr six speed with 3.21, and 35's. I was going to regear, and even bought a 44 front housing to upgrade. Sadly I bought a JK, and didn't realize the electronics in a bottom of the line sport were going to make it such a weak vehicle. I am regearing a 1994 XJ to replace the JK. Go by the chart. That is what I was going to do. I will down size the JK, and hopefully keep it as a daily driver. Gonna off road with a real Jeep.

Jfk70

The acceleration on the 5 speed is fine , top end is capped at about 80 mph but I only drive on the highway one day a week. I heard the 6 speed was a different situation. Lucky for me Florida is flatland so I don't need the manual tranny as much and there isn't much "hunting" for gears with the automatic.

Jonathan_JK

I don't know what your talking about... I have a strip down model with nothing upgraded from the factory but a CD player with XM and 3.73's and its not Electronically weak or whatever the hell your talking about.

Its called upgrading the Carriers to Eaton E-lockers and putting in an atlas T case. Also if you really want get a dual battery setup but its not necessary. I bolted all the aftermarket stuff up to my Jeep only thing I didn't do was paint the hood. I left that to the professionals.

metaldemon

Sir what I mean is all of the electronic issues I have had since new. I do use it as a Jeep. It has stuttered for a long time. Stuff turns on by itself, like the wipers. Runs really bad till I turn it off and back on, then it is OK. It will never do anything at the stealership. I have had far less issues with my two XJs.