MKempf

Thanks in advance:

I have a 2014 2-Door Wrangler Sport with a 6-Sppeed Manual Transmission and 3:73 Gears. I'm installing a 3.5" Suspension Lift and purchasing 35" Tires this is my daily driver so I use it on the Highway mostly with the occasional weekend off-road excursion. On weekend trips its going through the local back woods trails running through the mud holes and not a lot of rock climbing. I would like to know what gearing I should go with? I want to be able to use 6th gear on the Highway while getting the best gas mileage possible. (Yes I know its a jeep but if I can gain a few MPG's by using one set of gears compared to another then that needs to be part of the decision) and I also don’t want to rev the shit out of it to get moving with the bigger tires causing my clutch to burn up faster. If I have to spend the money on the gearing I don't want to get the wrong set up. I want a one and done scenario instead of well maybe I should of got this gear instead and have to drop more money. A middle of the road option is what I want. That is why I'm asking for this groups advice. Also I will not be going to 37" tires 35's are it. So I'm only concerned about 35's thank you for the help in advance.

resharp001

Well, the choice isn't as complicated as you can make it out to be really. The simple fact is that if you have 3.73, regearing to 4.10 isn't financially worthwhile. For a DD that doesn't do a lot of technical crawlin', your best bet is 4.56 for 35s (that will likely measure 34" or less) and you're 3.6L manual. Since you are primarily highway driving, 4.88s might be a little higher-revving at 70+mph speeds than you might prefer if you drive that fast. Granted, I have an auto, but my opinion is that 2500-2700 rpm at a 70mph cruising speed is the sweet spot for the 3.6L. That is not to say you won't ever have a moment you wished for one or the other, but you have to plan for 90% of your use and 4.56 is a bit more well-rounded for your scenario. Keep in mind the chart below relies on actual measurements of tire height. Measure from ground to center of hub and multiply by 2.

Creepy Neville

Resharp001 absolutely nailed it ....

1. Go with the 4.56's for about the same feel as you have now - but with 35" tires
2. Go with the 4.88's for the improved 'foot-to-ground' feel when you are offroading

To get some idea, go to your local dealer and take a JK Rubicon out around the block - the Rubicon will have 4.11's and 33" tires. I'm thinking you're gonna like the feel of the Rubicon - which would be pretty close to your truck equipped with 4.56's on 35's.

Having said that - in my opinion - go with the 4.88's, your JK will be a different animal - and you will LOVE it !

I run a 2016 JK / 6 speed with 40" tires (actually 38" when measured) and have 5.38 gearing - and I can do the speed limit with no issues ...

Neville

Sv_dude

All of these threads that talk about gears and gearing for the proper rpm at a given speed is leaving out a huge piece of the puzzle. Giving the roads, tires, elevation, etc… does the engine have the power to stay at the desired speed at the rpm. In my case, I’m a mile above sea level in the mountains. I can set my gears to run at a perfect rpm at 70mph, but our motors just don’t have the power to give at the perfect rpm to maintain that speed even with the differential gearing. I really feel like when you build a Jeep and regear it, you’re sacrificing economy. I need to be at 3500-4500 rpm to cruise at freeway speeds and that may mean I’m not in 5th gear. I like to think of it this way: regear your Jeep so you can cruise at freeway speeds and be within the power band of your engine so you can actually maintain speed. I can hypothetically put 10:1 gears in my diff and cruise at 80mph at 1500 rpm and get great mileage, but our engine has no power at that rpm. See where I’m going? Someone correct me if my line of thinking is wrong. I just don’t see out Jeeps maintaining much of any speed at 3k rpm and below unless you’re on flat ground at sea level.

Sixty4x4

Lots of good info here but remember even with gearing and tires increased in size and ratio to match something of stock setup for tires and gearing, the extra weight of the rotating mass has to be taken into account which really sucks power. Sv_Dude is right on the money here.

resharp001

My comment below is long-winded and might get a bit off topic, but generally this is all good conversation.

Sv_dude and I have very similar builds, similar tires, similar weight (I might be a little heavier with axle/wheel combination). I live just outside of Fort Worth and my driving is primarily highway-type speeds (if you’re not doing 75mph someone is on your ass). It’s relatively flat though winds out my direction can be very harsh. I’ve had various gearing/tire combinations during my build over the years and have “lived” in different RPM ranges. Opinions on performance are subjective, but I’ve never had complaints with my 3.6L with proper gearing for normal everyday use. I have found that cruising on the highway in the 2800-3000 rpm range to be completely acceptable in my mind (keep in mind that faster than the gear chart speed). At that RPM range my jeep maintains speed and can accelerate gradually if asked (I have an auto). If I need to pass someone on a multi-lane road it may shift down from 5th to 4th and I’m ok with that. That is typical of most non-performance cars. What is not acceptable to me is if it has to downshift from 5th to 3rd to have any guts to go (I am ok with this if having to pass someone on a 2-lane road and you really gotta put the pedal down to get around them, again, pretty normal for any vehicle I feel). The only time I’ve felt necessary to travel at 3500+ rpms just to maintain speed is when towing my camping trailer, but that isn’t normal everyday use in my mind, so it is what it is. I do keep in mind I’m driving a brick down the highway and my expectations are all relative to what I have built with every mod basically making it the least economical and ergonomic vehicle I possibly could. Does it get up and go like a sports car? No. Does it move the same way our Armada with a V8 does when you put your foot down? No. But for what it is it’s fine. My mindset when driving it is pretty different than any other car too though. I have much more relaxed attitude and an “I’ll get there when I get there” mindset. I do get to Colorado a decent bit to visit my dad and my jeep does ok. If I lived there full time I’d gear lower though for the mountains and lack of much high-speed interstate driving. Living in a geographic environment like that you’re revving at higher rpms regardless if you’re driving in 3rd/4th gear all the time with “norma gearing” through the mountains or 5th gear with lower gearing.

All that said, I feel I’ve built to about the max the 3.6L can handle and I can see how some feel that with 37s you need more HP with a V8 or forced induction. It’s just typically the tipping point. While building the jeep years ago I had friends that were on the same trajectory, but then they just kept going and going. I hit the brakes at 37” tires, primarily cuz I couldn’t get it in the garage with anything larger, but also because to go further was an even larger financial commitment and I also saw my buddies that went to 40s using their jeeps less and less as the enjoyment wained. Wheelin for them wasn’t as fun as they couldn’t find challenges, and their jeeps pretty much became trailer princesses. Then they just became happier driving their F250s everywhere due to a more comfortable ride. Anyhow, I digress. My issue with forced induction is though the extra HP is attractive, these mods are seldom seamless and have a lot of headaches. I’ve seen friends go through every turbo and super charger on the market and there were nagging issues with all of them, some direct issues and some indirect issues. I plan to keep my jeep forever so if this 3.6L ever dies the jeep might get a V8 and new lease on life, though I don’t feel skilled enough to handle that myself so it’s would be a big financial commitment. At this point I have 105k miles on my ’13, so that is likely a long way down the road.

Anyhow, with these gearing threads I try to keep in mind that most people are just looking to get their DD back to a normal performance after a few light mods like bumpers and tires, and that most people aren’t going out doing technical rock crawling that requires more aggressive lower gearing for the offroad benefit.

So, I get where Sv_dude is coming from. I’m a little surprised by the 3500-4500 rpm comment, but I also know he’s built right there on that tipping point I was talking about earlier.

Sixty4x4 has an interesting build with the V8 swap in an ’08 and with 33” tires if I recall. It’s not hard to wonder how you didn’t think the 3.8L was enough with 33s cuz that engine was so drastically underpowered, but you also have a 3.6L in the family, if I’m not mistaken. You have a unique view having seen performance with a 3.8L, the 3.6L, and your current V8. Curious for thoughts on the 3.6L in terms of being acceptable for most daily drivers with light mods.

Anyone going through the regear process does need to keep in mind the rolling mass commentary. Even if you skip 3 gear sets, it’s not like your jeep is going to feel like it’s got an extra 100+ HP, it’s just going to shift and drive better in general. You definitely can’t make up for horsepower with mechanical gearing.

Ryan0260

I would go with the 4.56 with the 35's. 4.88s will leave you turning pretty high rpms at interstate speeds if you do a lot of commuting.

sierradmax

Don't forget, your 35's will be more like 33-3/4" to 34".