wicked_pozer

Ok guys/gals. I've searched the forums until I couldn't search any more. I can't find any answers that are specific to my problem.

My rig: 2010 6spd 2 door Sport with, I assume, 3.21 gearing. It's a DD and I drive from Houston to NOLA and back every 2 weeks I recently went to 33's with a 2.5" RC coil lift. I'm liking the entire setup, except it completely DESTROYED my performance and gas mileage. Can't use 6th gear unless I get up to 75 MPH then I have to constantly downshift to make it up bridges, hills and through wind or to pass. I also have confirmed my speeds/distances with GPS

The computer said I was getting upwards of 22.1 MPG with the stock setup. Now the computer says I'm down around 15.1 most of the time and a recent highway trip proved to net me about 225 miles per tank!!! which is worse than what the computer estimated.

Now I don't mind 15.1 MPG.. but come on.. 12.2!?!?! seriously??

I'm thinking that the Jeep and I will be much happier with 4.10 gears. I would like to actually be able to accelerate in 6th gear and bump those MPG's back up to the 15-17 range with the possibility to maybe increase tire size in the future. Does this sound about right? This is my first Jeep, first 4x4. I'm mechanically inclined but it's all so new to me so I'd appreciate it soooooo much if I could get some advice from some of the REALLY experienced Jeepers.

Thanks for reading,

-K-

rexicon

33's with a 6 speed didn't kill your performance that bad if you started with 255 SRA's I'm surprised you could use 6th with your stock tires I couldn't unless going down hill. As for regearing do it once and go straight to 5.13. Yes I am running 35's on 3.21 in a 6 speed.

ps. the computer fuel estimator will be off with your larger tires as well as your speedometer and odometer

nthinuf

Stickied to the top of this modified area is a FAQ. In that faq is a Drivetrain area. In that drivetrain area is an RPM chart. Go outside and measure your tires (do not use mfg specs), and plug some numbers in.

My opinion, you would be wasting money to regear to a stock ratio. Plug in the numbers for 4.56's and see if that would be liveable. And if you have any plans of moving to 35's in the future, you might want to go even lower.

The other issue you are having is that you have not reprogrammed the computer for the new tire height. So you Speedo is off. Your ODO is off. And your Mileage is off. Get a ProCal or Flashpaq and recalibrate.

wicked_pozer

5.13's??? Dude, I'm not going to be doing any rock crawling here. Were you looking at the chart for the automatic trans? The manual tranny chart says I should be in the green (where I want to be) with the 4.10 gearing with either the 33's or the 35's. 33's will run at 2400-ish rpms with 4.10's. Am I understanding this correctly? I'd really like to find someone with this setup and ask them their opinion.

And, yes, I was able to accelerate in 6th gear on the highway with no problems. The RPM's were up to around 2,250 at 70 MPH.

wicked_pozer

Yes, I've checked the values with the GPS because I realized that the ODO and SPeedo would be off.

I don't think 4.56's would be a good fit for me. It would kill the MPG with the 33's, RPMs would rev too high at highway speeds.

Thanks for your input guys.

Stkman252

I didbasically the same as you with lift and 285/70/-17 bfg ta ko's. The stock 3:21s were terrible. I bought stock 4:10 from someone on this forum and am much happier. 6th gear is a usable gear now and it even accelerates in 6 th gear at 55mph. I now use my cruise control with 6 th gear. I would have to agree though with some of the other members that if you plan on going to tall 35s you might want to consider 4:56.

Rafi

i would do 4.88's if i were you. if you are going to spend the money and have someone install it. might as well do it the first time. then you have a reason to do 34-35's in a couple years..

dont think its too much gear. it might rev a little high, but it will give you a reason to use 6th more often and slow down on the highway. And people are just giving you their opions, you dont need to be defensive or try to make anyone feel bad because they suggested a gear ratio for you.

imo, minimum i would do 4.56, and i think if you keep the jeep, you will regret it and want 4.88's

i have 34's and im going to be doing 5.13's.

wicked_pozer

People often find my "tone" a little defensive, or offensive when I write, so for the purposes of this thread, I'll use the "tone notation = XXXX " designator.. probably in color yellow.

tone = inquisitive, friendly

I wasn't being defensive, funny maybe, but mostly confused.

Based on the chart that that one guy told me to reference, the gearing I want would put me in the green area at 2400 RPM with 4.10 gearing. I thought since the other guy was recommending 5.13, he may have been looking at the automatic trans chart by accident. I honestly feel that anything above 2500 RPM at 70MPH, based on my experiences with the stock tires, would be too high killing the MPGs. Oh, and what did you mean about ... and slow down on the highway? I have to go 75 or 80 on I-10 so I don't get run over by everyone else in Louisiana. So I'd like to keep under 2700 RPM to save a little fuel and still scoot.

Rafi, what gears are you running now? Have you driven any JK's with 33's or 35's that have re-geared to a lower ratio like the ones you've suggested?

wicked_pozer

tone = gracious, proud, and friendly

Thank you sir! I finally feel that someone read my first post in it's entirety, understood it and resounded my supporting ideas based on the conclusive evidence I found in the chart. I do A LOT of highway driving. The only offroading I can afford to do is to perpetuate my camping at the beach. (not that I can't afford to break things, but why would I?) I don't plan on abusing my DD and I don't want it to drive like carp. I just got tired of getting stuck at the beach, in buying the Jeep, I vowed to NEVER get stuck again. So it's a bit of a poseur... at least it's a Wicked Pozer

Edit: Just wanted to touch on the idea you had about the Rubi axles.. that's a GREAT idea by the way. I would definitely like to have lockers. This is very valuable information and I thank you.

bstpierre

You were getting 22.1 MPG going 75 or 80 MPH? Were you drafting?

I had a 2 door X with the 29 inch tires and I was finally getting about 20 MPG after I slowed down to 65 MPH on the freeway. I find people have no problem going around me. I do find it awkward when I have to pass someone.