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Love my 3:21's!

3K views 39 replies 24 participants last post by  64cyclone 
#1 ·
Drove from Virginia Beach to West Virginia today. Cruise set at 72 mph and averaged 23.2 mpg all uphill! The auto did downshift on a couple of steep mountains but keep the speed right where it was set during all 340 miles.
 
#3 ·
I'm getting more use to mine everyday. I got a few stretches of highway that are pretty hilly that I do slap it in forth and leave it. The auto just doesn't like anything under 2k pulling hills. I've noticed I'm getting slightly better MPG driving it this way also.
 
#7 ·
Just took the wifes new Sahara Unlimited to Florida and back. 75 mph there and back from Illinois. 21.5 mpg. I was pleased and it drove very well. Plenty of power when needed and very respectable millage for shoving a brick in the wind.
 
#8 ·
Can't say I agree with the OP. I hated the way my jeep felt with the 3.21s. I regeared to 4.10, and my overall average fuel economy over the last 3 tanks is 19.6mpg. On the highway, I'll do 22mpg on a trip no problem. A small price to pay for way better performance.
 
#9 ·
Loving mine too. Averaging over 20 on every tank. If you're happy, I'm happy. We're all driving Wranglers, most set up just the way we want them. That the beauty if these things, we can make them for ourselves!
 
#11 ·
Cruise set at 72 mph and averaged 23.2 mpg all uphill! The auto did downshift on a couple of steep mountains but keep the speed right where it was set during all 340 miles.
Same here, 3.21 and auto and we love it. We don't live in the Rockies, will never have larger tires on it and no lift. Thus, the combination is perfect.

The pic below was after an hour on cruise control on the highway, driving into a slight headwind. We were thinking about taking it on our drive from St. Louis to Yellowstone in a few weeks but my Sebring gets slightly better mpg.

 
#17 ·
This might have a lot to do with it. I drove both 3.21's and 3.73's and there was no comparison on the 4dr, the 3.73's kicked the 3.21's ass...

2dr on 3.21's with no other mods and running in highway mode, might be just fine.
 
#14 ·
I don't mind mine but will be much happier when the 4.56's and rear locker is in. I didn't buy my jeep for highway or mileage. I'm also looking foward to using 5th & 6th gear more often.

With 3.21's I got a best of 22.5 mpg on a trip to Va but I'm rarely on the highway so I think I'll benefit more with 4.56's for around town and off road.
 
#15 ·
I've got 3.21's on a stock 2014 JKU Sport. Never seen anything more than about 19 MPG. I'm at sea level and flat. I did notice two things 1) offroad at the beach you really have to use high rpms and work the clutch 2) pulling a 3500 lb trailer you really need to use the clutch and rpms to start out and 6th gear is really not useable

I ordered a 2015 with an automatic and 3.72's so I'll see how it works out. Only difference is that it has the offroad tires vs. the street tires on the sport.
 
#16 ·
Like the op I have 3.21's and for now they are good enough. 20-23 mpg on the highway in town 16-17 not as good but still better then my 2008 gmc was now all that being said if I end up keeping this Jeep for an extended period of time I'm will look into going to 4.10's because I won't go any bigger in tires then 33"-35" as for now I just got 225/75/17 duratracs. I do wish I wouldn't have got in such a hurry a the dealership and would have got 3.73 with LSD. In the last three years I had 2010 JKU sport S for about 8 months then an 2008 gmc Sierra 1500 Z71 for 18 and now a 2014 JKU sport S for two I hope I don't get the itch to change vehicles and just keep modding this Jeep.
 
#23 ·
Fuel mileage was absolutely a factor for me. I previously had an Xterra that had the supercharged engine. That thing got 11 mpg at 75 mph. I was basically making a car payment with the amount of gas I was wasting. Same reason I didn't look at a Hummer or any of the other offroad type vehicles that get terrible fuel mileage. Jeep found a way to get surprisingly decent fuel mileage and still retain all the style and capabilities. Plus the resale on Jeeps is tremendous.
 
#28 ·
Something I have noticed, no actual data but something that I see popping up a lot when talking about MPGs: 3.73s seem to have the worst mileage, and the 3.21s and 4.10s better mileage and are often similar. 3.21s a little better on the highway and the 4.10 a little better in town. I am assuming stock or close to stock tires. Anyone else seeing this trend?
 
#29 ·
I'm not sure about the 3.73s, but I was surprised how little difference in average fuel economy I get between 3.21 and 4.10. (On stock Sahara tires that is) Definitely not enough to worry about. Changing tire weight/width affects mileage far more than the ratio does.
 
#31 ·
I'm averaging 16-17. That's combining around town and my 8 mile commute one way to work @ 65. 255/75 trail grappers and a flashpaq set on 87 octane. 3.21's. The more I drive learning its shift patterns and manual down shifting when needed seems its getting a little better. I blame the heavy Nittos and using ethanol fuel (all we have here) on the slightly less mileage than some of yall.
 
#40 ·
My Jeep (with 3.21s) isn't in yet, but I did have the opportunity to drive a 6 spd with 3.21s. No real issues other than it sure doesn't feel like 285 hp. I expected more power. More than my old 4 cyl 5spd Liberty, but nothing to write home about.
 
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