Got 5 275/70/18's installed yesterday and I love how they look and perform, however i've lost alot more power on the highway than I thought I would. I have a 6 spd Sahara Unlimited with 3.21's, i'm running the tires at 33 PSI with Spidertrax spacers on stock wheels. It's an absolute dog on the highway now, cant even maintain 100 km/h in 5th gear have to shift to 4th if the incline is even remotely steep. I do have a Superchips and was wondering if that would make any difference if I used the 87 tune with 89 octane fuel? I'm seriously looking at re-gearing right now more than anything, I thought 3.21's would be sufficient enough to run 33's but I definitley thought wrong, what should I go to if I re-gear? 4.10's seem like a waste, 4.88's seem like the way to go.

 

If you plan on sticking with 33's, go with 4.56's. Even if you go to 35's 4.56's will work fine for you. But it will give you better HWy RPM than 4.88's. Plus the pinion is bigger and less likely to break in the little D30.

 

Really? I always thought the higher the number the better the RPM. Thanks for the info!

 

I think you have 3.73's.

 

As far as I know the 3.73's only came with the tow package in the '08 6spd Sahara's, I didnt buy the tow package lol.

 

The pinion is bigger but "better" RPM is subjective to the driver. The consensus in this forum for the manual is the 4.88 is the optimum gear ratio for 35s and power is already an issue so biasing towards fuel economy may not be the best choice.

 

you are correct. the 3.73's came on tow packages on 2008-up JK's. if you didn't get this, you have 3.21's.

as far as regearing goes, honestly, i would highly recommend 4.88's. sure your rpm's will be on the higher side of things but, just by a bit and the boost in power you'll get will make you quite happy.

 

i did same thing... but with 285/75/16's
big power loss yeah.. but once i put exhaust intake hypertech shes a whole new animal..

but still a dog

 

Well, to each their own, but with 4.88's and 33's they will be running 3k RPM on the HWY. To me that is unacceptably high and results in very high drive shaft speeds.

4.56's would be better suited for 33's. And if they do go to 35's one day, is still plenty livable with a 6sp. 4.56's with 35's is still far better gearing than 3.21's with the stock 29" tires.

 

I stand corrected, I thought all Sahara's had the tow package standard.

I agree with the 4.56. I got a deal on a set of 4.10's that I couldn't pass up. ($75 - and installed for $300 + the cost of front carrier and install kits )

I lived with 35's (KM2's only 34") and 3.21's for about a year and it was livable with the 6sp.

But the 4.10's make it much more fun to drive. Because I didn't drop a load of cash for the swap
and I can get the labor cheap, I may still do a 4.56 or 4.88 later.


Intake = a lil more, Exhaust = not sure, but fun to drive. All three together maybe.
But you need to look at Superchips if your looking for a programmer.