There are people who experience an mpg gain after re-gearing. That's because there original gears were so far off with the advent of new tires they were outside of the power-band and their Jeep was continually hunting for gears and under powered for the amount of meat they were spinning. That is primarily the automatic crowd, and not so likely with the 6 speed unless someone forces use of 6th gear when they have too much tire for it and to little gear.

With a manual transmission you should have a pretty good feel for where your gears need to be before you invest in them. Highway cruise speeds/rpms, where you need to down shift for hills and are you jumping down two gears or just a single one. To me the drawback would be if I had gears so steep that I needed be cranking my rpms above 2500 at 70 mph, although my Jeep is probably a couple hundred pounds lighter than yours.

Drive a few days without 6th gear. Do you think you're twisting the engine to hard? Are you happy with your acceleration from a standing start? Need to use the brakes too much when descending a hill on the trail?

Bottom line is that you don't need to give up much in mpg unless you really want to pound it out of the hole. Also think if your future has 37s in it.

 

Need to compare gas mileage in similar temperatures. If you're looking at winter mileage versus summer mileage, it's going to distort your results. Vehicles take a lot longer to get up to operating temperatures and use more fuel until they do. My guess is that you can split the difference of your before and after numbers. Also, you can't save fuel by cruising at less than 2,000rpm.

 

Gears seem like a monstrous investment, but it seems like everyone here has regeared.
Where do you get gears?
Can you regear yourself?
Where do you go to have new gearing installed?

I'm just wondering.
I think the tonka could be even more beastly with different gearing ratio.

 

Doubt it. Sgt. Evil statement was completely inaccurate. Whether or not your mileage will go up or down depends on allot of factors -- some of which were mentioned. Your build, powerband, driving habit, etc. are all relevant.

When I lifted I went down and when I regeared I went back up to a bit shy of stock.

 

Depending on the ratio your looking for, you can scrounge the Sales section here and find some take out 4.10's for a great deal. Or refer to forum recommended vendors.
YES YOU CAN. Currently running an on going thread on this myself.
Look around your local area for recommended driveline shops knowledgeable with installing gears in our JK's...be prepared to spend $$

To answer the MPG question. To a point tall gears (numerically lower) will serve to get you better MPG...until you throw bigger tires on, then you sacrafice MPG to get them turning, re-gearing to a smaller gear(numerically higher) can improve MPG, again to a point, it's really a balancing act. The second you threw bigger tires on you threw stock mileage out the window and won't get it back, but you can come close to your stock performance...it's really a balancing act and the right gear ratio with your 35's will net you reasonable mileage with reasonable performance.

 

Now I have conflicting advice! lol I know my stock gas mileage is out the window, but always want to get the best that IS possible still.

If I can restore power AND restore gas mileage a little(even if it is a small gain of only 1 or 2) then regearing to 4.88s is definately worth it.

If I am only going to worsen my gas mileage then it may not be worth it......

I feel conflicted.

 

have a look at this to get some kind of an idea of what happens with tires and gear changes....
http://www.superioraxle.com/feature.html

 

Gee, Then let me say this, yes depends on your driving habits, where you live, freeway or city.

MY EXPERIENCE WAS WHEN I REGEARED I LOST MILLAGE AND S DID A LOT OF PEOPLE I KNOW> SO THE GEARING ALONG WITH UPGRADES CAUSED A MPG LOSS>NOT EVEN CLOSE TO MY STOCK MPG> SO YOU WERE LUCKY GETTING CLOSE TO YOUR MPG> BUT NOT ME OR PEOPLE I KNOW>

is that better.

SO I GUESS IT"S NOT COMPLETELY INACCURATE<

 

What is your RPM at 80mph? Just curious

 

If you are rolling at much less than 2,000 rpm at any given speed you are wasting fuel. This engine simply doesn't make good power below that point and you don't do yourself any favors by cruising around at 1500 rpm in terms of fuel economy.