River Runner

i HAD (as of next week) (getten gears changed)an auto with 33's and 4.10, you will hate that you spent your money on 4.10's. They suck im not in the best shape but i believe i could out run a jeep with 33's , 4.10's on a bicycle from a red light. and the mpg suck as well. Skip that 4.56 shit and go with the 4.88 you wont be sorry, and 35's are doable with that gear set up. just my experience. the chart just above my post is SPOT on that is the exact rpm with auto 32/33 tires and 4.10

Mark Doiron

Trying to get reliable data on gas mileage is nigh impossible. The gentleman immediately after your original post has 4.10s, an auto and 33s and gets 21-22 MPG. I'm running 4.10s, a six speed and 33s and am extremely diligent about checking gas mileage: 16 MPG. Others will quote you even lower and even higher gas mileage for similar configurations, so really whatever mileage you get is just something you'll need to live with.

What you should concentrate on is getting optimal performance from what little torque/horsepower your Jeep delivers. And, as has already been pointed out, an important factor in all of this is that you own an auto (for the record, I read your profile immediately after reading your question, before reading any of the replies--because it's important to know that before even attempting to answer your question). Anyway, running the 4.10 gears, a six speed and 33" tires (which actually measure in at 31.25" and when placed next to a stock Rubi with stock tires appear to be even smaller than its 32s!), I'm only modestly satisfied with the performance. Situations where I wish I had more ooomph are primarily on the Interstate: When driving up hills, when driving into heavy winds, when carrying heavy gear (fully loaded down), I almost always find the vehicle's performance lacking. If I were driving an auto, the performance would be even worse, and my satisfaction even less.

Other than that, I'm not driving a race car and the Jeep's performance is entirely okay. Therefore, I wish that I had one notch up in gearing--to 4.56s. If I were driving an auto, I'd be even more dissatisfied, especially since with a six speed I can push it down to 5th, 4th and yes even 3rd gear!! on the Interstate to try to maintain my speed. An auto is going to be doing this with a mind of its own, and there are plenty of testimonials on this forum that it will drive you nuts. Therefore, I'd push up an additional notch for the automatic and 33s: 4.88s. I think that will provide you optimal highway performance from what that little 3.8L can deliver.

Adam3612

Oops my bad, forgot to check his profile out to see what he has. I just kind of assumed it was manual if he was looking at 4.10's or 4.56's lol.
P.S. Since when did the auto's start getting 3.21's? I thought my 6 speed was gutless with 3.21's, couldnt imagine an auto.

Mark Doiron

He may not have 3.21s. According to the 2007 factory brochure (his profile says he has an '07), the autos all came with 4.10s. But, who knows what Chrysler may have done on the production line when they had a part and a hole it would fit into? I always suggest to folks that the best way to determine what they really have is to lift the vehicle and rotate the tire and count driveshaft revolutions. That takes into account Chrysler's on-the-line production changes, aftermarket parts, etc.

nthinuf

One of the many annoying little tidbits I have seen is that some 07 2door auto's came with 3.21, but all 07 4door auto's came with 4.10. And then we could ask him to double check whether he is sure he has a d44 rear, instead of being one of the extremely lucky folks that ended up with a d35 rear. (no clue what gears or transmissions he actually has, was just going by his profile that says auto and his first post that says 3.21's...)

It is difficult trying to nail down all of the variations in how these things are built.

defierro

I'm sorry I'm a jeep newby. My jeep did in fact have 4.10 gear ratio! Thanks guys!

Jeepforfun

I know this is an old post that has been reserected, but you don't always have to regear for 33's. I can understand the desire for that, if you have the factory 3.21's. But my point is that you don't have to go up to 4.88's or 5.13's just to run 33's. I believe that you could get by on 4.10's or 4.56's for 33's and probably for 35's if your primary use is a daily driver. IF your primamry use is extreme off road then you should be putting the money towards a D44 or D60 front anyway.

I am currently running 33/11.50's (285/70-16 Nitto's) with the automatic and stock 3.73's I have no problem with drivability and drive about 80 miles a day on the interstate. I get an average of 16.5 - 17 MPG on winter blend gas and about 17.5 on summer blend. If I do much running around downtown then it does drop a couple of MPG. This is without speedometer correction for the tire size.

I ran 33/12'50's on SEVERAL of the previous Wranglers I have owned with the way underpowered 123 HP 4 cylinder and stock gears; I would only loose the use of 5th gear on the interstate with that set up. But had no other problems with it. This is the first Jeep I have ever owned that would do 85MPH with 33's.

You get into other problems with extreme lower gears that the pinion is too small and supceptable to breakage expecially on the stock Dana 30 front axle. Up until recently you could only get 4.56's for the D30. Some of the problems I see lot's posts about on this forum are related to overgearing and too large of a tire on a weak front axle. The rule of thumb that us old Jeepsers used was a max 35" tire on the D30 (4.56) and 38's on the D44 (4.88). If you wanted to go lower or bigger you need to move up to D60's or Rockwell's.