My experience with JLU Sport with auto, 3.43 gears, Mopar 2" lift and 33" AT tires

[mwilk012]

Your dealer is either lazy or incompetent. Not only will your speedometer be off but your transmission shift points as well.

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[wrangster]

Doubt you needed a lift when a wheel spacer could have worked well. Those tires actually are 32.7" just short of true 33's and lifts give more issues over time. If you are not rock climbing or heavy mudding that rig sell the lift kit back and regain some mileage you lost.

 

[SpringsJL]

I’m rocking a sport on 35s with mopar lift you need make sure your speedo is calibrated. My gas mileage is good IMO $20 a week for last 6 months can’t complain. Far as transmission it does wind up little more upgrading to 4.10s would be perfect for 35s.

 

[Moto_21]

I’m rocking a sport on 35s with mopar lift you need make sure your speedo is calibrated. My gas mileage is good IMO $20 a week for last 6 months can’t complain. Far as transmission it does wind up little more upgrading to 4.10s would be perfect for 35s.

Do you think 4.10s or 4.56? Im trying to figure outfor myself as well.

 

[SpringsJL]

4.10 should do it my only trouble is going up hills wants to slow down some. May never upgrade unless find a good deal.

 

[WXman]

Keep in mind that the 3.6L engine hates cold weather. They drink gas pretty bad when it gets cold outside. That's been my experience with 3 of them in 3 different vehicles. A bigger loss than the average vehicle sees. Also, we're on winterized fuel now. We probably weren't when you first got your Jeep.

So, if you calibrate your speedometer and wait until spring, I bet you'll be within 2 MPG of where the Jeep was when it was bone stock.

Mine went from 20 average to around 18 average after the lift and tires. Most guys with stock Rubicons are getting what I am getting right now, so I don't believe the 4.10 gears help any.

 

[rizzkid]

there is no need to regear with an 8 speed trans. The 8 speed ratios are much lower in 1-2 gear than the previous generation trans. 33 inch tires should be no issue. As other have stated, recalibrate for the larger tires as your MPG is not accurate. As a minimum disconnect the battery so the trans can "re-learn: the new shiftpoints with the larger tires.
I did this with my 2013 Ram with the same trans, same 3.6l engine with 33 tires and I akways used 8th gear on the highway. In addition the Ram only had 3.21 gears! The Ram1500 is also heavier, 4x4 quad cab 6.5 bed model

Gear Ratios for 8 speed tranny 2018 JL
1st 4.71
2nd 3.13
3rd 2.10
4th 1.67
5th 1.28
6th 1.00
7th 0.84
8th 0.67
Reverse 3.53

2012 -2017 JK
1st 3.59
2nd 2.19
3rd 1.41
4th 1
5th 0.83
Reverse 3.16

 

[George999]

Keep in mind that the 3.6L engine hates cold weather. They drink gas pretty bad when it gets cold outside. That's been my experience with 3 of them in 3 different vehicles. A bigger loss than the average vehicle sees. Also, we're on winterized fuel now. We probably weren't when you first got your Jeep.

So, if you calibrate your speedometer and wait until spring, I bet you'll be within 2 MPG of where the Jeep was when it was bone stock.

Mine went from 20 average to around 18 average after the lift and tires. Most guys with stock Rubicons are getting what I am getting right now, so I don't believe the 4.10 gears help any.

I was wonder about the cold weather, So my JL was used, the owner before me added the Rubi wheels, tires, and RC 2.5" lift. when i first got it i was getting almost 19 mgh, Then i noticed slowly losing MPG. At one point i was getting like 15 MPG but noticed the air pressure in the tires where all over the place. Right now i am keeping the tires at 36 psi and getting about 17.5 not the best for ride but not really all that bad either. I also thought about removing the lift as i will not be rock climbing but really like the look. I know the tazer can set the tire size, however does that mean you have to leave in the bypass? I wonder if i need to have mne set.

 

[larkja]

I have the exact same setup minus the lift. I have the JL Tazer and have recalibrated for the larger tires. I average 18mpg around town and 20 to 22 on the hwy. 8th gear is a pipe dream above 70 mph.

 

[Shots]

If you didnt calabrate for
Tires your mpg will be off.

Yeah, good point. 31 to 33 is a 6% increase in size. With that in mind the odometer is reading 6% less miles than actually traveled so the mpg calculations are going to also be 6% off. It's not a huge difference, but a difference just the same. If you figure a calculated 15 mpg the actual would be 1 mpg better.

Doubt you needed a lift when a wheel spacer could have worked well. Those tires actually are 32.7" just short of true 33's and lifts give more issues over time. If you are not rock climbing or heavy mudding that rig sell the lift kit back and regain some mileage you lost.

For 33's, I doubt a spacer would have even necessary. A lot of people who are installing 2 or 2.5" lifts don't need them. For some people (me included) they simply what the look and/or higher ride provided by a small lift. It's not a concern of ground clearance, or even of clearing bigger tires. For a lot of people mild lifts are an aesthetic modification more than anything. Sure they may provide more clearance, but that's usually more like a bonus than the intent. Obviously that's not everyone, but it seems to be a fair amount. Sounds like the OP is in that group.

 

[ThirtyOne]

So I put 285/70r17 on my Sport S. Same size as Rubicon. No lift. I have compared it up to about 45MPH against a roadside speed sign and it matched.

Is it really necessary to calibrate? How do I explain to my dealer how to do it? I find I need to give them very specific instructions.

Thanks!

 

[2500 hd]

I have a JLU sport s. Mopar lift and 35's. Getting 15-16. Has not been recalibrated.
Rides good , shifts good. I dig it !!!!

 

[Shots]

So I put 285/70r17 on my Sport S. Same size as Rubicon. No lift. I have compared it up to about 45MPH against a roadside speed sign and it matched.

Is it really necessary to calibrate? How do I explain to my dealer how to do it? I find I need to give them very specific instructions.

Thanks!

Adjusting is recommended, but you can get by without doing it. If you went from stock 245/70/17 to 285/70/17 you're looking at a 7.2% difference in tire size. As a result your speedometer (and odometer) are off by the same 7.2%. If the speedometer shows 45 mph you're actually traveling 48 mph, which isn't a huge deal. However, since it's a percentage the faster you go the more distinct the difference which can land you in hot water (ie: speeding ticket). Assuming a trip down the interstate, if your speedometer shows 70 mph you're actually driving 75 mph. Again not the biggest issue, but you're 5 over the limit when you think your right at it. Most people tend to drive between 5-10 over the posted limit which then puts you 10-15 over the limit. I think we all know that 10-15 over is usually enough to get a speeding ticket, which is why most people aim for 5 ish.
So long story short, if you don't adjust it, make sure you keep the speedometer AT or below the posted limit (which you should to anyway), because you're going faster than it says.

As for telling the dealer how to adjust it. Plug into the OBDII port with their flash tool and change the tire size. Very straight forward. If they can't figure something that simple out I wouldn't want them touching my Jeep for anything.

 

[Trauma PA]

This is my experience with a JLU sport with auto tranny,3.43 gears, Mopar 2" lift and 33" 285/70r17 AT tires. So , I wanted a little better off road performance and love the lifted ,leveled look with oversized tires. Just what everyone wants.Before I started down this road, the JLU would get about 25mpg, while running in 8th gear and taching somewhere around 1500 rpm. The ride was very smooth with the stock tires. Yesterday was my first trip with any real milage . I think it was around 250 miles total. Anyone else thinking of doing this exact thing or going with even bigger tires than 33's, please read on. While everyone with a Rubicon will be quite happy with 33's or larger, they have 4.10 gears. With the 3.43 gears, 8th gear is only a momentary thing at highway speeds above 55 as it shfits right back to 7th. You might can manually shift it to 8th, but it can't stay there as it will start slowing down at 72 or above. I get between 13 and 15 mph while in 7th gear and running 70. I found I could get 18 or so if I tailgate an 18 wheeler. I burnt a whole tank of gas and the avg mpg was 16.3mpg. Running 55mph , the JL will occasionally try 8th gear for about a mile or so until there is a uphill grade or a head wind, it then goes to 7th. It will also tend to want to remain in 6th at times. This might be acceptable to some, but with all the other problems I have had this is not acceptable for me. I would have expected this to happen if I had gone with 35s or bigger but 33s are minimally larger than stock. I am considering taking the 2" lift back off. I would get back that smooth ride and maybe 8th gear. The reason I think this might work is that I know that after the lift but before the tires, the JL lost 8th gear. I did a test drive right after the lift. There is nothing short of regearing going to fix this. If anyone else has a setup like this, what is your gas milage and have you seen 8th gear lately? I wish I would have gotten a Rubicon or just stayed away from Jeeps all together.

I feel your pain. But not enough to want to get rid of my Jeep. I've been driving Wranglers since 1988 and keep on coming back to them despite the less than optimal fuel economy. It's a sacrifice that I'm willing to make as it's the only vehicle I've ever owned that puts a smile on my face on a regular basis.

To give you another perspective, I too have the 2" Mopar lift on my Jeep paired with Black Rhino Barstows and Mastercraft Courser Mud Terrains which are just shy of 35." The combined weight for my wheel + tire package is 97 lb. My combined city + highway fuel economy is between 16.5 and 16.8 mpg. I drive between 75-80 mph. If I decrease my highway speed to around 72 mph on cruise control I can eek out 17 mpg. As you know, our Jeeps are nothing more than bricks traveling down the highway, especially with a lift kit on. There is nothing aerodynamic about a Wrangler. I just accept it and smile every time I get in my Jeep.

 

[Yoyo27983]

I'm confused. What vehicle would you get other than a Jeep that you would add a 2-inch lift, 33 inch tires, and get better gas mileage?

I'm not sure the Rubicon would be any better. The gearing is better for power but not MPG and it is heavier.

I did not expect it to drop from 25 to 16mpg. That was a shock. And I did not expect it to be geared such that it can't stay in 8th gear even if you mash on it to try to maintain the current speed. The lift made a bigger difference in mpg than I expected. I don't remember reading about the mpg cost of lifts anywhere. I guess I will get used to it, maybe. I would like to hear what the Rubicons are getting, I'm curious now. I do think that the Rubicon is geared to better handle bigger tires , more so than the sport. Maybe they did try to engineer every single mpg out of this model. Even to the point of running thin oil as I have seen others post. If you find and read my other post about all the problems I have had , maybe you could understand why I feel like this after spending that much money only to find out I get to now regear, trade up for a Rubi, take off the lift, or just be satisfied with what it is. This is not my first jeep but it will be my last.

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